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TUCoPS :: Unix :: General :: beginunx.txt

A beginner's Guide to Unix by Brian Kernighan of Bell Labs


             UUUUNNNNIIIIXXXX FFFFoooorrrr BBBBeeeeggggiiiinnnnnnnneeeerrrrssss----SSSSeeeeccccoooonnnndddd EEEEddddiiiittttiiiioooonnnn

                     Brian W. Kernighan

                     Bell Laboratories

               Murray Hill, New Jersey 07974


       This paper  is  meant  to  help  new  users  get
     started  on  the  UNIX*  operating   system.    It

      o+basics needed for day-to-day use of the system -
       typing  commands,  correcting  typing  mistakes,
       logging in and out, mail, inter-terminal commun-
       ication,   the   file  system,  printing  files,
       redirecting I/O, pipes, and the shell.

      o+document preparation - a brief discussion of the
       major  formatting  programs  and macro packages,
       hints  on  preparing  documents,   and   capsule
       descriptions of some supporting software.

      o+UNIX programming - using the editor, programming
       the shell, programming in C, other languages and

      o+An annotated UNIX bibliography.


  From the user's point of view, the UNIX  operating  system

is  easy  to  learn  and  use, and presents few of the usual

impediments to getting the job done.  It is  hard,  however,

* UNIX is a Trademark of Bell Laboratories.

                     November 16, 1985

2                                         _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

for the beginner to know where to start, and how to make the

best  use  of the facilities available.  The purpose of this

introduction is to help new users get used to the main ideas

of  the  UNIX  system  and  start making effective use of it


  You should have a couple of other documents with  you  for

easy  reference as you read this one.  The most important is

_T_h_e _U_N_I_X _P_r_o_g_r_a_m_m_e_r'_s _M_a_n_u_a_l; it's often easier to tell  you

to  read  about  something  in the manual than to repeat its

contents here.  The other  useful  document  is  _A  _T_u_t_o_r_i_a_l

_I_n_t_r_o_d_u_c_t_i_o_n  _t_o  _t_h_e  _U_N_I_X _T_e_x_t _E_d_i_t_o_r, which will tell you

how to use the editor to get text -  programs,  data,  docu-

ments - into the computer.

  A word of warning: the UNIX system has become quite  popu-

lar, and there are several major variants in widespread use.

Of course details also change with time.   So  although  the

basic  structure  of UNIX and how to use it is common to all

versions, there will certainly be a  few  things  which  are

different  on  your  system from what is described here.  We

have tried to minimize the problem, but be aware of it.   In

cases of doubt, this paper describes Version 7 UNIX.

  This paper has five sections:

  1.Getting Started: How to log in, how to type, what to  do

  about mistakes in typing, how to log out.  Some of this is

  dependent on which system you log into (phone numbers, for

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                         3

  example)  and  what terminal you use, so this section must

  necessarily be supplemented by local information.

  2.Day-to-day Use: Things you need every  day  to  use  the

  system  effectively:  generally  useful commands; the file


  3.Document Preparation: Preparing manuscripts  is  one  of

  the  most common uses for UNIX systems.  This section con-

  tains advice, but not extensive instructions on any of the

  formatting tools.

  4.Writing  Programs:  UNIX  is  an  excellent  system  for

  developing programs.  This section talks about some of the

  tools, but again is not a tutorial in any of the  program-

  ming languages provided by the system.

  5.A UNIX Reading List.  An annotated bibliography of docu-

  ments that new users should be aware of.

_I.  _G_E_T_T_I_N_G _S_T_A_R_T_E_D

_L_o_g_g_i_n_g _I_n

  You must have a UNIX login name, which you  can  get  from

whoever  administers your system.  You also need to know the

phone number, unless your system uses permanently  connected

terminals.   The  UNIX  system  is capable of dealing with a

wide variety of terminals: Terminet 300's; Execuport, TI and

similar  portables;  video  (CRT) terminals like the HP2640,

etc.; high-priced  graphics  terminals  like  the  Tektronix

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4                                         _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

4014;  plotting  terminals like those from GSI and DASI; and

even the venerable Teletype in its various forms.  But note:

UNIX  is  strongly oriented towards devices with _l_o_w_e_r _c_a_s_e.

If your terminal produces only upper case  (e.g.,  model  33

Teletype,  some  video and portable terminals), life will be

so difficult that you should look for another terminal.

  Be sure to set the switches appropriately on your  device.

Switches  that  might need to be adjusted include the speed,

upper/lower case mode, full duplex,  even  parity,  and  any

others  that  local  wisdom advises.  Establish a connection

using whatever magic is needed for your terminal;  this  may

involve  dialing  a  telephone  call  or  merely  flipping a

switch.  In either case, UNIX should type ``llllooooggggiiiinnnn::::'' at you.

If  it  types  garbage, you may be at the wrong speed; check

the switches.  If that fails, push the ``break'' or ``inter-

rupt''  key a few times, slowly.  If that fails to produce a

login message, consult a guru.

  When you get a llllooooggggiiiinnnn:::: message, type  your  login  name  _i_n

_l_o_w_e_r  _c_a_s_e.   Follow it by a RETURN; the system will not do

anything  until  you  type  a  RETURN.   If  a  password  is

required, you will be asked for it, and (if possible) print-

ing will be turned off while  you  type  it.   Don't  forget


  The culmination of your login efforts is a ``prompt  char-

acter,''  a  single character that indicates that the system

is ready to accept commands from you.  The prompt  character

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is  usually  a  dollar sign $$$$ or a percent sign %%%%.  (You may

also get a message of the day just before the prompt charac-

ter, or a notification that you have mail.)

_T_y_p_i_n_g _C_o_m_m_a_n_d_s

  Once you've seen the prompt character, you can  type  com-

mands, which are requests that the system do something.  Try



followed by RETURN.  You should get back something like

  MMMMoooonnnn JJJJaaaannnn 11116666 11114444::::11117777::::11110000 EEEESSSSTTTT 1111999977778888

Don't forget the RETURN after the command, or  nothing  will

happen.   If  you think you're being ignored, type a RETURN;

something should happen.  RETURN won't be  mentioned  again,

but  don't forget it - it has to be there at the end of each


  Another command you might try  is  wwwwhhhhoooo,  which  tells  you

everyone who is currently logged in:


gives something like

  mmmmbbbb   ttttttttyyyy00001111JJJJaaaannnn 11116666    00009999::::11111111
  sssskkkkiiii  ttttttttyyyy00005555JJJJaaaannnn 11116666    00009999::::33333333
  ggggaaaammmm  ttttttttyyyy11111111JJJJaaaannnn 11116666    11113333::::00007777

The time is when  the  user  logged  in;  ``ttyxx''  is  the

system's idea of what terminal the user is on.

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6                                         _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

  If you make a mistake typing the command name,  and  refer

to  a  non-existent command, you will be told.  For example,

if you type


you will be told

  wwwwhhhhoooommmm:::: nnnnooootttt ffffoooouuuunnnndddd

Of course, if you inadvertently type the name of some  other

command, it will run, with more or less mysterious results.

_S_t_r_a_n_g_e _T_e_r_m_i_n_a_l _B_e_h_a_v_i_o_r

  Sometimes you can get into a  state  where  your  terminal

acts  strangely.   For  example,  each  letter  may be typed

twice, or the RETURN may not cause a line feed or  a  return

to  the  left margin.  You can often fix this by logging out

and logging back in.  Or you can read the description of the

command ssssttttttttyyyy in section I of the manual.  To get intelligent

treatment of tab characters (which are much used in UNIX) if

your terminal doesn't have tabs, type the command

  ssssttttttttyyyy ----ttttaaaabbbbssss

and the system will convert each tab into the  right  number

of  blanks  for  you.   If your terminal does have computer-

settable tabs, the command ttttaaaabbbbssss will set the stops correctly

for you.

_M_i_s_t_a_k_e_s _i_n _T_y_p_i_n_g

  If you make a typing mistake, and see it before RETURN has

                     November 16, 1985

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been  typed,  there  are  two  ways  to recover.  The sharp-

character #### erases the last character typed; in fact succes-

sive uses of #### erase characters back to the beginning of the

line (but not beyond).   So  if  you  type  badly,  you  can

correct as you go:


is the same as ddddaaaatttteeee.

  The at-sign @@@@ erases all of the characters typed so far on

the  current  input  line,  so  if the line is irretrievably

fouled up, type an @@@@ and start the line over.

  What if you must enter a sharp or at-sign as part  of  the

text?   If  you  precede  either #### or @@@@ by a backslash \\\\, it

loses its erase meaning.  So to enter a sharp or at-sign  in

something,  type  \\\\####  or  \\\\@@@@.  The system will always echo a

newline at you after your at-sign, even  if  preceded  by  a

backslash.  Don't worry - the at-sign has been recorded.

  To erase a backslash, you have to type two sharps  or  two

at-signs,  as  in \\\\########.  The backslash is used extensively in

UNIX to indicate that the following character is in some way



  UNIX has full read-ahead, which means that you can type as

fast  as you want, whenever you want, even when some command

is typing at you.  If you type  during  output,  your  input

                     November 16, 1985

8                                         _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

characters  will  appear  intermixed with the output charac-

ters, but they will be stored away and  interpreted  in  the

correct  order.   So you can type several commands one after

another without waiting for the  first  to  finish  or  even


_S_t_o_p_p_i_n_g _a _P_r_o_g_r_a_m

  You can stop most programs by typing the character ``DEL''

(perhaps  called ``delete'' or ``rubout'' on your terminal).

The ``interrupt'' or ``break'' key found on  most  terminals

can  also be used.  In a few programs, like the text editor,

DEL stops whatever the program is doing but  leaves  you  in

that program.  Hanging up the phone will stop most programs.

_L_o_g_g_i_n_g _O_u_t

  The easiest way to log out is to hang up the  phone.   You

can also type


and let someone else use the terminal you were  on.   It  is

usually  not sufficient just to turn off the terminal.  Most

UNIX systems do not use a time-out mechanism, so  you'll  be

there forever unless you hang up.


  When you log in, you may sometimes get the message

  YYYYoooouuuu hhhhaaaavvvveeee mmmmaaaaiiiillll....

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_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                         9

UNIX provides a postal system so you  can  communicate  with

other users of the system.  To read your mail, type the com-



Your mail will be printed,  one  message  at  a  time,  most

recent  message  first.   After each message, mmmmaaaaiiiillll waits for

you to say what to do with it.  The two basic responses  are

dddd, which deletes the message, and RETURN, which does not (so

it will still be there the next time you read your mailbox).

Other  responses are described in the manual.  (Earlier ver-

sions of mmmmaaaaiiiillll do not process one message at a time, but  are

otherwise similar.)

  How do you send mail to someone else?  Suppose it is to go

to  ``joe'' (assuming ``joe'' is someone's login name).  The

easiest way is this:

  mmmmaaaaiiiillll jjjjooooeeee
  _n_o_w _t_y_p_e _i_n _t_h_e _t_e_x_t _o_f _t_h_e _l_e_t_t_e_r
  _o_n _a_s _m_a_n_y _l_i_n_e_s _a_s _y_o_u _l_i_k_e ...
  _A_f_t_e_r _t_h_e _l_a_s_t _l_i_n_e _o_f _t_h_e _l_e_t_t_e_r
  _t_y_p_e _t_h_e _c_h_a_r_a_c_t_e_r ``_c_o_n_t_r_o_l-_d'',
  _t_h_a_t _i_s, _h_o_l_d _d_o_w_n ``_c_o_n_t_r_o_l'' _a_n_d _t_y_p_e
  _a _l_e_t_t_e_r ``_d''.

And that's it.  The  ``control-d''  sequence,  often  called

``EOF''  for  end-of-file,  is used throughout the system to

mark the end of input from a terminal, so you might as  well

get used to it.

  For practice, send  mail  to  yourself.   (This  isn't  as

strange  as it might sound - mail to oneself is a handy rem-

                     November 16, 1985

10                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

inder mechanism.)

  There are other ways to send mail - you can send a  previ-

ously  prepared letter, and you can mail to a number of peo-

ple all at once.  For more details see mmmmaaaaiiiillll(1).  (The  nota-

tion mmmmaaaaiiiillll(1) means the command mmmmaaaaiiiillll in section 1 of the _U_N_I_X

_P_r_o_g_r_a_m_m_e_r'_s _M_a_n_u_a_l.)

_W_r_i_t_i_n_g _t_o _o_t_h_e_r _u_s_e_r_s

  At some point, out of the blue will come a message like

  MMMMeeeessssssssaaaaggggeeee ffffrrrroooommmm jjjjooooeeee ttttttttyyyy00007777............

accompanied by a startling beep.  It means that Joe wants to

talk  to  you, but unless you take explicit action you won't

be able to talk back.  To respond, type the command

  wwwwrrrriiiitttteeee jjjjooooeeee

This establishes a two-way communication path.  Now whatever

Joe  types  on  his  terminal  will appear on yours and vice

versa.  The path is slow, rather like talking to  the  moon.

(If you are in the middle of something, you have to get to a

state where you can type a command.  Normally, whatever pro-

gram  you are running has to terminate or be terminated.  If

you're editing, you can escape temporarily from the editor -

read the editor tutorial.)

  A protocol is needed to keep what you  type  from  getting

garbled up with what Joe types. Typically it's like this:

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        11

  Joe types wwwwrrrriiiitttteeee ssssmmmmiiiitttthhhh and waits.
  Smith types wwwwrrrriiiitttteeee jjjjooooeeee and waits.
  Joe now types his message (as many  lines  as  he  likes).
  When  he's ready for a reply, he signals it by typing ((((oooo)))),
  which stands for ``over''.
  Now Smith types a reply, also terminated by ((((oooo)))).
  This cycle repeats  until  someone  gets  tired;  he  then
  signals  his  intent  to  quit  with  ((((oooooooo)))), for ``over and
  To terminate the  conversation,  each  side  must  type  a
  ``control-d''  character alone on a line. (``Delete'' also
  works.) When the other person types his ``control-d'', you
  will get the message EEEEOOOOFFFF on your terminal.

  If you write to  someone  who  isn't  logged  in,  or  who

doesn't want to be disturbed, you'll be told.  If the target

is logged in but doesn't answer  after  a  decent  interval,

simply type ``control-d''.

_O_n-_l_i_n_e _M_a_n_u_a_l

  The _U_N_I_X _P_r_o_g_r_a_m_m_e_r'_s _M_a_n_u_a_l is  typically  kept  on-line.

If  you  get stuck on something, and can't find an expert to

assist you, you can print on your terminal some manual  sec-

tion  that  might help.  This is also useful for getting the

most up-to-date information on a command.  To print a manual

section,  type ``man command-name''.  Thus to read up on the

wwwwhhhhoooo command, type

  mmmmaaaannnn wwwwhhhhoooo

and, of course,

  mmmmaaaannnn mmmmaaaannnn

tells all about the mmmmaaaannnn command.

                     November 16, 1985

12                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

_C_o_m_p_u_t_e_r _A_i_d_e_d _I_n_s_t_r_u_c_t_i_o_n

  Your UNIX system  may  have  available  a  program  called

lllleeeeaaaarrrrnnnn, which provides computer aided instruction on the file

system and basic commands, the editor, document preparation,

and even C programming.  Try typing the command


If lllleeeeaaaarrrrnnnn exists on your system, it will tell you what to  do

from there.

_I_I.  _D_A_Y-_T_O-_D_A_Y _U_S_E

_C_r_e_a_t_i_n_g _F_i_l_e_s - _T_h_e _E_d_i_t_o_r

  If you have to type a paper or a letter or a program,  how

do  you  get the information stored in the machine?  Most of

these tasks are done  with  the  UNIX  ``text  editor''  eeeedddd.

Since  eeeedddd is thoroughly documented in eeeedddd(1) and explained in

_A _T_u_t_o_r_i_a_l _I_n_t_r_o_d_u_c_t_i_o_n _t_o _t_h_e _U_N_I_X _T_e_x_t  _E_d_i_t_o_r,  we  won't

spend  any  time here describing how to use it.  All we want

it for right now is to make some _f_i_l_e_s.  (A file is  just  a

collection  of information stored in the machine, a simplis-

tic but adequate definition.)

  To create a file called jjjjuuuunnnnkkkk with some text in it, do  the


  eeeedddd jjjjuuuunnnnkkkk(invokes the text editor)
  aaaa     (command to ``ed'', to add text)
  _n_o_w _t_y_p_e _i_n
  _w_h_a_t_e_v_e_r _t_e_x_t _y_o_u _w_a_n_t ...
  ....     (signals the end of adding text)

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        13

The ``....'' that signals the end of adding text must be at the

beginning  of  a line by itself.  Don't forget it, for until

it is typed, no other  eeeedddd  commands  will  be  recognized  -

everything you type will be treated as text to be added.

  At this point you can do various editing operations on the

text  you  typed  in,  such as correcting spelling mistakes,

rearranging paragraphs and  the  like.   Finally,  you  must

write  the  information  you have typed into a file with the

editor command wwww:


eeeedddd will respond with the number of characters it wrote  into

the file jjjjuuuunnnnkkkk.

  Until the wwww command, nothing is stored permanently, so  if

you hang up and go home the information is lost.|- But  after

wwww the information is there permanently; you can re-access it

any time by typing

  eeeedddd jjjjuuuunnnnkkkk

Type a qqqq command to quit the editor.  (If you  try  to  quit

without  writing, eeeedddd will print a ???? to remind you.  A second

qqqq gets you out regardless.)

  Now create a second file called tttteeeemmmmpppp in the  same  manner.

You should now have two files, jjjjuuuunnnnkkkk and tttteeeemmmmpppp.
|- This is not strictly true -  if  you  hang  up  while
editing,  the  data  you  were working on is saved in a
file called eeeedddd....hhhhuuuupppp, which you can continue with at your
next session.

                     November 16, 1985

14                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

_W_h_a_t _f_i_l_e_s _a_r_e _o_u_t _t_h_e_r_e?

  The llllssss (for ``list'') command lists the  names  (not  con-

tents)  of  any  of the files that UNIX knows about.  If you



the response will be


which are indeed the two files just created.  The names  are

sorted  into  alphabetical  order  automatically,  but other

variations are possible.  For example, the command

  llllssss ----tttt

causes the files to be listed in the  order  in  which  they

were last changed, most recent first.  The ----llll option gives a

``long'' listing:

  llllssss ----llll

will produce something like

  ----rrrrwwww----rrrrwwww----rrrrwwww---- 1111 bbbbwwwwkkkk 44441111 JJJJuuuullll 22222222 2222::::55556666 jjjjuuuunnnnkkkk
  ----rrrrwwww----rrrrwwww----rrrrwwww---- 1111 bbbbwwwwkkkk 77778888 JJJJuuuullll 22222222 2222::::55557777 tttteeeemmmmpppp

The date and time are of the last change to the  file.   The

41  and  78 are the number of characters (which should agree

with the numbers you got from eeeedddd).  bbbbwwwwkkkk is the owner of  the

file,  that  is,  the person who created it.  The ----rrrrwwww----rrrrwwww----rrrrwwww----

tells who has permission to read and write the file, in this

case everyone.

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        15

  Options can be combined: llllssss ----lllltttt gives the  same  thing  as

llllssss ----llll,  but  sorted  into time order.  You can also name the

files you're interested in, and llllssss will list the information

about them only.  More details can be found in llllssss(1).

  The use of optional arguments  that  begin  with  a  minus

sign,  like ----tttt and ----lllltttt, is a common convention for UNIX pro-

grams.  In general, if a program accepts such optional argu-

ments,  they  precede  any  filename  arguments.  It is also

vital that you separate the various arguments  with  spaces:

llllssss----llll is not the same as llllssss  ----llll.

_P_r_i_n_t_i_n_g _F_i_l_e_s

  Now that you've got a file of text, how do you print it so

people can look at it?  There are a host of programs that do

that, probably more than are needed.

  One simple thing is to use the editor, since  printing  is

often done just before making changes anyway.  You can say

  eeeedddd jjjjuuuunnnnkkkk

eeeedddd will reply with the count of the characters in  jjjjuuuunnnnkkkk  and

then  print  all the lines in the file.  After you learn how

to use the editor, you can be selective about the parts  you


  There are times when it's not feasible to use  the  editor

for  printing.   For  example, there is a limit on how big a

file eeeedddd can handle (several thousand lines).   Secondly,  it

                     November 16, 1985

16                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

will  only  print one file at a time, and sometimes you want

to print several, one after another.  So here are  a  couple

of alternatives.

  First is ccccaaaatttt, the simplest of all the  printing  programs.

ccccaaaatttt  simply  prints  on the terminal the contents of all the

files named in a list.  Thus

  ccccaaaatttt jjjjuuuunnnnkkkk

prints one file, and

  ccccaaaatttt jjjjuuuunnnnkkkk tttteeeemmmmpppp

prints two.  The files are simply  concatenated  (hence  the

name ``ccccaaaatttt'') onto the terminal.

  pppprrrr produces formatted printouts of files.  As with ccccaaaatttt, pppprrrr

prints  all  the  files  named in a list.  The difference is

that it produces headings with date, time, page  number  and

file  name  at the top of each page, and extra lines to skip

over the fold in the paper.  Thus,

  pppprrrr jjjjuuuunnnnkkkk tttteeeemmmmpppp

will print jjjjuuuunnnnkkkk neatly, then skip to the top of a  new  page

and print tttteeeemmmmpppp neatly.

  pppprrrr can also produce multi-column output:

  pppprrrr ----3333 jjjjuuuunnnnkkkk

prints jjjjuuuunnnnkkkk in 3-column format.  You can use any  reasonable

number  in  place  of ``3'' and pppprrrr will do its best.  pppprrrr has

other capabilities as well; see pppprrrr(1).

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        17

  It should be noted that pppprrrr is _n_o_t a formatting program  in

the  sense of shuffling lines around and justifying margins.

The true formatters are nnnnrrrrooooffffffff and ttttrrrrooooffffffff, which we  will  get

to in the section on document preparation.

  There are also programs that print files on  a  high-speed

printer.   Look  in your manual under oooopppprrrr and llllpppprrrr.  Which to

use depends on what equipment is attached to your machine.

_S_h_u_f_f_l_i_n_g _F_i_l_e_s _A_b_o_u_t

  Now that you have some files in the file system  and  some

experience in printing them, you can try bigger things.  For

example, you can move a  file  from  one  place  to  another

(which amounts to giving it a new name), like this:

  mmmmvvvv jjjjuuuunnnnkkkk pppprrrreeeecccciiiioooouuuussss

This means that what used  to  be  ``junk''  is  now  ``pre-

cious''.  If you do an llllssss command now, you will get


Beware that if you move a file to another one  that  already

exists, the already existing contents are lost forever.

  If you want to make a _c_o_p_y of a file (that is, to have two

versions of something), you can use the ccccpppp command:

  ccccpppp pppprrrreeeecccciiiioooouuuussss tttteeeemmmmpppp1111

makes a duplicate copy of pppprrrreeeecccciiiioooouuuussss in tttteeeemmmmpppp1111.

  Finally, when you get tired of creating and moving  files,

                     November 16, 1985

18                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

there  is  a  command  to remove files from the file system,

called rrrrmmmm.

  rrrrmmmm tttteeeemmmmpppp tttteeeemmmmpppp1111

will remove both of the files named.

  You will get a warning message if one of the  named  files

wasn't  there,  but  otherwise  rrrrmmmm, like most UNIX commands,

does its work silently.  There is no prompting  or  chatter,

and error messages are occasionally curt.  This terseness is

sometimes disconcerting to newcomers, but experienced  users

find it desirable.

_W_h_a_t'_s _i_n _a _F_i_l_e_n_a_m_e

  So far we have used filenames without ever saying what's a

legal  name,  so  it's  time  for a couple of rules.  First,

filenames are limited to 14 characters, which is  enough  to

be  descriptive.   Second,  although  you can use almost any

character in a filename, common sense says you should  stick

to ones that are visible, and that you should probably avoid

characters that might be used with other meanings.  We  have

already  seen,  for  example,  that in the llllssss command, llllssss ----tttt

means to list in time order.  So if you  had  a  file  whose

name was ----tttt, you would have a tough time listing it by name.

Besides the minus sign, there  are  other  characters  which

have  special meaning.  To avoid pitfalls, you would do well

to use only letters, numbers and  the  period  until  you're

familiar with the situation.

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        19

  On to some more positive suggestions.  Suppose you're typ-

ing  a  large  document like a book.  Logically this divides

into many small pieces, like chapters and perhaps  sections.

Physically  it  must  be divided too, for eeeedddd will not handle

really big files.  Thus you should type the  document  as  a

number  of  files.   You might have a separate file for each

chapter, called


Or, if each chapter were  broken  into  several  files,  you

might have


You can now tell at a glance where a  particular  file  fits

into the whole.

  There are advantages to  a  systematic  naming  convention

which  are not obvious to the novice UNIX user.  What if you

wanted to print the whole book?  You could say

  pppprrrr cccchhhhaaaapppp1111....1111 cccchhhhaaaapppp1111....2222 cccchhhhaaaapppp1111....3333 ........................

but you would get tired pretty fast, and would probably even

make  mistakes.   Fortunately, there is a shortcut.  You can


  pppprrrr cccchhhhaaaapppp****

                     November 16, 1985

20                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

The **** means ``anything at all,''  so  this  translates  into

``print  all  files whose names begin with cccchhhhaaaapppp'', listed in

alphabetical order.

  This shorthand notation is not a property of the  pppprrrr  com-

mand,  by the way.  It is system-wide, a service of the pro-

gram that interprets commands (the ``shell,'' sssshhhh(1)).  Using

that fact, you can see how to list the names of the files in

the book:

  llllssss cccchhhhaaaapppp****



The **** is not limited to the last position in a filename - it

can be anywhere and can occur several times.  Thus

  rrrrmmmm ****jjjjuuuunnnnkkkk**** ****tttteeeemmmmpppp****

removes all files that contain jjjjuuuunnnnkkkk or tttteeeemmmmpppp as any  part  of

their  name.   As  a special case, **** by itself matches every

filename, so

  pppprrrr ****

prints all your files (alphabetical order), and

  rrrrmmmm ****

removes _a_l_l _f_i_l_e_s.  (You had better be _v_e_r_y sure that's what

you wanted to say!)

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        21

  The **** is not the only pattern-matching feature  available.

Suppose  you  want to print only chapters 1 through 4 and 9.

Then you can say

  pppprrrr cccchhhhaaaapppp[[[[11112222333344449999]]]]****

The [[[[............]]]] means to match any of the  characters  inside  the

brackets.   A  range of consecutive letters or digits can be

abbreviated, so you can also do this with

  pppprrrr cccchhhhaaaapppp[[[[1111----44449999]]]]****

Letters can also be used within brackets: [[[[aaaa----zzzz]]]] matches  any

character in the range aaaa through zzzz.

  The ???? pattern matches any single character, so

  llllssss ????

lists all files which have single-character names, and

  llllssss ----llll cccchhhhaaaapppp????....1111

lists information about  the  first  file  of  each  chapter

(cccchhhhaaaapppp1111....1111, cccchhhhaaaapppp2222....1111, etc.).

  Of these niceties, **** is certainly the most useful, and you

should  get  used  to  it.  The others are frills, but worth


  If you should ever have to turn off the special meaning of

****, ????, etc., enclose the entire argument in single quotes, as


  llllssss ''''????''''

                     November 16, 1985

22                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

We'll see some more examples of this shortly.

_W_h_a_t'_s _i_n _a _F_i_l_e_n_a_m_e, _C_o_n_t_i_n_u_e_d

  When you first made that file called  jjjjuuuunnnnkkkk,  how  did  the

system  know  that there wasn't another jjjjuuuunnnnkkkk somewhere else,

especially since the person in the next office is also read-

ing  this  tutorial?  The answer is that generally each user

has a private _d_i_r_e_c_t_o_r_y, which contains only the files  that

belong  to him.  When you log in, you are ``in'' your direc-

tory.  Unless you take special action, when you create a new

file, it is made in the directory that you are currently in;

this is most often your own directory, and thus the file  is

unrelated  to  any  other  file  of the same name that might

exist in someone else's directory.

  The set of all files is organized  into  a  (usually  big)

tree,  with  your  files  located  several branches into the

tree.  It is possible for you to ``walk'' around this  tree,

and  to find any file in the system, by starting at the root

of the tree and walking along the proper  set  of  branches.

Conversely,  you can start where you are and walk toward the


  Let's try the latter first.  The basic tools is  the  com-

mand  ppppwwwwdddd  (``print  working  directory''), which prints the

name of the directory you are currently in.

  Although the details will vary according to the system you

are on, if you give the command ppppwwwwdddd, it will print something

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        23



This says that you are currently in the directory yyyyoooouuuurrrr----nnnnaaaammmmeeee,

which  is in turn in the directory ////uuuussssrrrr, which is in turn in

the root directory called by convention just  ////.   (Even  if

it's  not called ////uuuussssrrrr on your system, you will get something

analogous.  Make the corresponding changes and read on.)

  If you now type

  llllssss ////uuuussssrrrr////yyyyoooouuuurrrr----nnnnaaaammmmeeee

you should get exactly the same list of file  names  as  you

get  from  a  plain llllssss: with no arguments, llllssss lists the con-

tents of the current directory; given the name of  a  direc-

tory, it lists the contents of that directory.

  Next, try

  llllssss ////uuuussssrrrr

This should print a long series of  names,  among  which  is

your  own  login  name yyyyoooouuuurrrr----nnnnaaaammmmeeee.  On many systems, uuuussssrrrr is a

directory that contains the directories of  all  the  normal

users of the system, like you.

  The next step is to try

  llllssss ////

You should get a  response  something  like  this  (although

again the details may be different):

                     November 16, 1985

24                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s


This is a collection of the basic directories of files  that

the system knows about; we are at the root of the tree.

  Now try

  ccccaaaatttt ////uuuussssrrrr////yyyyoooouuuurrrr----nnnnaaaammmmeeee////jjjjuuuunnnnkkkk

(if jjjjuuuunnnnkkkk is still around in your directory).  The name


is called the ppppaaaatttthhhhnnnnaaaammmmeeee of the file that you  normally  think

of  as  ``junk''.   ``Pathname''  has an obvious meaning: it

represents the full name of the path you have to follow from

the root through the tree of directories to get to a partic-

ular file.  It is a universal rule in the UNIX  system  that

anywhere  you  can  use  an ordinary filename, you can use a


  Here is a picture which may make this clearer:

                            / | \
                           /  |  \
                          /   |   \
                bin    etc    usr    dev   tmp
            / | \   / | \   / | \   / | \   / | \
                           /  |  \
                          /   |   \
                       adam  eve   mary
                   /        /   \        \
                            /     \       junk
                          junk temp

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        25

Notice that Mary's jjjjuuuunnnnkkkk is unrelated to Eve's.

  This isn't too exciting if all the files of  interest  are

in  your own directory, but if you work with someone else or

on several projects concurrently, it becomes  handy  indeed.

For example, your friends can print your book by saying

  pppprrrr ////uuuussssrrrr////yyyyoooouuuurrrr----nnnnaaaammmmeeee////cccchhhhaaaapppp****

Similarly, you can find out what files your neighbor has  by


  llllssss ////uuuussssrrrr////nnnneeeeiiiigggghhhhbbbboooorrrr----nnnnaaaammmmeeee

or make your own copy of one of his files by

  ccccpppp ////uuuussssrrrr////yyyyoooouuuurrrr----nnnneeeeiiiigggghhhhbbbboooorrrr////hhhhiiiissss----ffffiiiilllleeee yyyyoooouuuurrrrffffiiiilllleeee

  If your neighbor doesn't want you  poking  around  in  his

files,  or  vice  versa, privacy can be arranged.  Each file

and directory has  read-write-execute  permissions  for  the

owner,  a group, and everyone else, which can be set to con-

trol access.  See llllssss(1) and  cccchhhhmmmmoooodddd(1)  for  details.   As  a

matter  of  observed  fact, most users most of the time find

openness of more benefit than privacy.

  As a final experiment with pathnames, try

  llllssss ////bbbbiiiinnnn ////uuuussssrrrr////bbbbiiiinnnn

Do some of the names look familiar?  When you run a program,

by  typing  its  name after the prompt character, the system

simply looks for a file of that  name.   It  normally  looks

first  in  your  directory  (where it typically doesn't find

                     November 16, 1985

26                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

it), then in ////bbbbiiiinnnn and finally in ////uuuussssrrrr////bbbbiiiinnnn.  There is nothing

magic  about  commands like ccccaaaatttt or llllssss, except that they have

been collected into a couple of places to be  easy  to  find

and administer.

  What if you work regularly with  someone  else  on  common

information in his directory?  You could just log in as your

friend each time you want to, but you can also say ``I  want

to  work  on his files instead of my own''.  This is done by

changing the directory that you are currently in:

  ccccdddd ////uuuussssrrrr////yyyyoooouuuurrrr----ffffrrrriiiieeeennnndddd

(On some systems, ccccdddd is spelled cccchhhhddddiiiirrrr.) Now when you  use  a

filename  in something like ccccaaaatttt or pppprrrr, it refers to the file

in your friend's directory.   Changing  directories  doesn't

affect  any  permissions  associated  with  a  file - if you

couldn't access a file from your own directory, changing  to

another  directory won't alter that fact.  Of course, if you

forget what directory you're in, type


to find out.

  It is usually convenient to arrange your own files so that

all  the  files  related  to  one  thing  are in a directory

separate from other projects.  For example, when  you  write

your  book,  you might want to keep all the text in a direc-

tory called bbbbooooooookkkk.  So make one with

  mmmmkkkkddddiiiirrrr bbbbooooooookkkk

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        27

then go to it with

  ccccdddd bbbbooooooookkkk

then start typing  chapters.   The  book  is  now  found  in



To remove the directory bbbbooooooookkkk, type

  rrrrmmmm bbbbooooooookkkk////****
  rrrrmmmmddddiiiirrrr bbbbooooooookkkk

The first command removes all files from the directory;  the

second removes the empty directory.

  You can go up one level in the tree of files by saying

  ccccdddd ........

``........'' is the name of the parent of whatever  directory  you

are  currently  in.  For completeness, ``....'' is an alternate

name for the directory you are in.

_U_s_i_n_g _F_i_l_e_s _i_n_s_t_e_a_d _o_f _t_h_e _T_e_r_m_i_n_a_l

  Most of the commands we have seen so far produce output on

the  terminal;  some, like the editor, also take their input

from the terminal.  It is universal in UNIX systems that the

terminal  can  be  replaced  by a file for either or both of

input and output.  As one example,


makes a list of files on your terminal.  But if you say

                     November 16, 1985

28                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

  llllssss >>>>ffffiiiilllleeeelllliiiisssstttt

a list of your files will be placed  in  the  file  ffffiiiilllleeeelllliiiisssstttt

(which  will  be  created  if  it  doesn't already exist, or

overwritten if it does).  The symbol >>>> means ``put the  out-

put  on  the  following file, rather than on the terminal.''

Nothing is produced on the terminal.   As  another  example,

you  could  combine  several files into one by capturing the

output of ccccaaaatttt in a file:

  ccccaaaatttt ffff1111 ffff2222 ffff3333 >>>>tttteeeemmmmpppp

  The symbol >>>>>>>> operates very much like >>>> does, except  that

it means ``add to the end of.'' That is,

  ccccaaaatttt ffff1111 ffff2222 ffff3333 >>>>>>>>tttteeeemmmmpppp

means to concatenate ffff1111, ffff2222 and ffff3333 to the end of whatever is

already  in  tttteeeemmmmpppp,  instead of overwriting the existing con-

tents.  As with >>>>, if tttteeeemmmmpppp doesn't exist, it will be created

for you.

  In a similar way, the symbol <<<< means to take the input for

a  program from the following file, instead of from the ter-

minal.  Thus, you could make up a script  of  commonly  used

editing  commands  and  put  them into a file called ssssccccrrrriiiipppptttt.

Then you can run the script on a file by saying

  eeeedddd ffffiiiilllleeee <<<<ssssccccrrrriiiipppptttt

As another example, you can use eeeedddd to prepare  a  letter  in

file lllleeeetttt, then send it to several people with

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        29

  mmmmaaaaiiiillll aaaaddddaaaammmm eeeevvvveeee mmmmaaaarrrryyyy jjjjooooeeee <<<<lllleeeetttt


  One of the novel contributions of the UNIX system  is  the

idea  of a _p_i_p_e.  A pipe is simply a way to connect the out-

put of one program to the input of another program,  so  the

two run as a sequence of processes - a pipeline.

  For example,

  pppprrrr ffff gggg hhhh

will print the files ffff, gggg, and hhhh, beginning each  on  a  new

page.   Suppose  you  want  them  run together instead.  You

could say

  ccccaaaatttt ffff gggg hhhh >>>>tttteeeemmmmpppp
  pppprrrr <<<<tttteeeemmmmpppp
  rrrrmmmm tttteeeemmmmpppp

but this is more work than necessary.  Clearly what we  want

is  to take the output of ccccaaaatttt and connect it to the input of

pppprrrr.  So let us use a pipe:

  ccccaaaatttt ffff gggg hhhh |||| pppprrrr

The vertical bar |||| means to take the output from ccccaaaatttt,  which

would normally have gone to the terminal, and put it into pppprrrr

to be neatly formatted.

  There are many other examples of pipes.  For example,

  llllssss |||| pppprrrr ----3333

prints a list of your files in three columns.   The  program

                     November 16, 1985

30                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

wwwwcccc  counts  the number of lines, words and characters in its

input,  and  as  we  saw  earlier,  wwwwhhhhoooo  prints  a  list  of

currently-logged on people, one per line.  Thus

  wwwwhhhhoooo |||| wwwwcccc

tells how many people are logged on.  And of course

  llllssss |||| wwwwcccc

counts your files.

  Any program that reads from the terminal can read  from  a

pipe  instead;  any  program that writes on the terminal can

drive a pipe.  You can have as many elements in  a  pipeline

as you wish.

  Many UNIX programs are written  so  that  they  will  take

their  input  from  one  or more files if file arguments are

given; if no arguments are given they  will  read  from  the

terminal,  and  thus  can  be  used in pipelines.  pppprrrr is one


  pppprrrr ----3333 aaaa bbbb cccc

prints files aaaa, bbbb and cccc in order in three columns.  But in

  ccccaaaatttt aaaa bbbb cccc |||| pppprrrr ----3333

pppprrrr prints the information coming down the pipeline, still in

three columns.

_T_h_e _S_h_e_l_l

  We have already mentioned once  or  twice  the  mysterious

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        31

``shell,'' which is in fact sssshhhh(1).  The shell is the program

that interprets what you type as commands and arguments.  It

also   looks  after  translating  ****,  etc.,  into  lists  of

filenames, and <<<<, >>>>, and |||| into changes of input and  output


  The shell has other capabilities too.   For  example,  you

can run two programs with one command line by separating the

commands with a semicolon; the shell  recognizes  the  semi-

colon and breaks the line into two commands.  Thus

  ddddaaaatttteeee;;;; wwwwhhhhoooo

does both commands before returning with a prompt character.

  You can also have more than one program running _s_i_m_u_l_t_a_n_e_-

_o_u_s_l_y  if you wish.  For example, if you are doing something

time-consuming, like the editor script of  an  earlier  sec-

tion,  and  you  don't  want  to wait around for the results

before starting something else, you can say

  eeeedddd ffffiiiilllleeee <<<<ssssccccrrrriiiipppptttt &&&&

The ampersand at the end of a command line says ``start this

command  running, then take further commands from the termi-

nal immediately,'' that is, don't wait for it  to  complete.

Thus the script will begin, but you can do something else at

the same time.  Of course, to keep the output from interfer-

ing  with  what  you're  doing  on the terminal, it would be

better to say

  eeeedddd ffffiiiilllleeee <<<<ssssccccrrrriiiipppptttt >>>>ssssccccrrrriiiipppptttt....oooouuuutttt &&&&

                     November 16, 1985

32                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

which saves the output lines in a file called ssssccccrrrriiiipppptttt....oooouuuutttt.

  When you initiate a command with  &&&&,  the  system  replies

with  a  number  called the process number, which identifies

the command in case you later want to stop it.  If  you  do,

you can say

  kkkkiiiillllllll pppprrrroooocccceeeessssssss----nnnnuuuummmmbbbbeeeerrrr

If you forget the process number, the command ppppssss  will  tell

you   about  everything  you  have  running.   (If  you  are

desperate, kkkkiiiillllllll 0000 will kill  all  your  processes.)  And  if

you're  curious about other people, ppppssss aaaa will tell you about

_a_l_l programs that are currently running.

  You can say

  ((((ccccoooommmmmmmmaaaannnndddd----1111;;;; ccccoooommmmmmmmaaaannnndddd----2222;;;; ccccoooommmmmmmmaaaannnndddd----3333)))) &&&&

to start three commands in the background, or you can  start

a background pipeline with

  ccccoooommmmmmmmaaaannnndddd----1111 |||| ccccoooommmmmmmmaaaannnndddd----2222 &&&&

  Just as you can tell the editor or some similar program to

take its input from a file instead of from the terminal, you

can tell the shell to read a file  to  get  commands.   (Why

not?  The  shell,  after  all,  is  just a program, albeit a

clever one.) For instance, suppose you want to set  tabs  on

your terminal, and find out the date and who's on the system

every time you log in.  Then you can put the three necessary

commands  (ttttaaaabbbbssss,  ddddaaaatttteeee,  wwwwhhhhoooo)  into  a  file,  let's call it

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        33

ssssttttaaaarrrrttttuuuupppp, and then run it with

  sssshhhh ssssttttaaaarrrrttttuuuupppp

This says to run the shell with the file ssssttttaaaarrrrttttuuuupppp  as  input.

The effect is as if you had typed the contents of ssssttttaaaarrrrttttuuuupppp on

the terminal.

  If this is to be a regular thing, you  can  eliminate  the

need to type sssshhhh: simply type, once only, the command

  cccchhhhmmmmoooodddd ++++xxxx ssssttttaaaarrrrttttuuuupppp

and thereafter you need only say


to run the sequence of commands.  The cccchhhhmmmmoooodddd(1) command marks

the  file  executable; the shell recognizes this and runs it

as a sequence of commands.

  If you want ssssttttaaaarrrrttttuuuupppp to run automatically  every  time  you

log  in,  create  a  file  in  your  login  directory called

....pppprrrrooooffffiiiilllleeee, and place in it the line ssssttttaaaarrrrttttuuuupppp.  When the  shell

first  gains  control  when  you  log  in,  it looks for the

....pppprrrrooooffffiiiilllleeee file and does whatever commands  it  finds  in  it.

We'll get back to the shell in the section on programming.

_I_I_I. _D_O_C_U_M_E_N_T _P_R_E_P_A_R_A_T_I_O_N

  UNIX systems are used extensively  for  document  prepara-

tion.   There  are  two  major formatting programs, that is,

programs that produce a text with justified  right  margins,

                     November 16, 1985

34                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

automatic page numbering and titling, automatic hyphenation,

and the like.  nnnnrrrrooooffffffff is designed to produce output on termi-

nals  and  line-printers.   ttttrrrrooooffffffff  (pronounced ``tee-roff'')

instead drives a phototypesetter, which produces  very  high

quality  output  on photographic paper.  This paper was for-

matted with ttttrrrrooooffffffff.

_F_o_r_m_a_t_t_i_n_g _P_a_c_k_a_g_e_s

  The basic idea of nnnnrrrrooooffffffff and ttttrrrrooooffffffff is that the text  to  be

formatted  contains  within  it ``formatting commands'' that

indicate in detail how the formatted text is to  look.   For

example, there might be commands that specify how long lines

are, whether to use single or double spacing, and what  run-

ning titles to use on each page.

  Because nnnnrrrrooooffffffff and ttttrrrrooooffffffff are relatively hard  to  learn  to

use  effectively,  several ``packages'' of canned formatting

requests are available to let you specify  paragraphs,  run-

ning titles, footnotes, multi-column output, and so on, with

little effort and without having to learn nnnnrrrrooooffffffff  and  ttttrrrrooooffffffff.

These  packages  take  a  modest  effort  to  learn, but the

rewards for using them are so great that  it  is  time  well


  In this section, we will  provide  a  hasty  look  at  the

``manuscript''  package  known  as ----mmmmssss.  Formatting requests

typically consist of a period and  two  upper-case  letters,

such  as  ....TTTTLLLL, which is used to introduce a title, or ....PPPPPPPP to

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        35

begin a new paragraph.

  A document is typed so it looks something like this:

  ttttiiiittttlllleeee ooooffff ddddooooccccuuuummmmeeeennnntttt
  aaaauuuutttthhhhoooorrrr nnnnaaaammmmeeee
  sssseeeeccccttttiiiioooonnnn hhhheeeeaaaaddddiiiinnnngggg
  ppppaaaarrrraaaaggggrrrraaaapppphhhh ............
  aaaannnnooootttthhhheeeerrrr ppppaaaarrrraaaaggggrrrraaaapppphhhh ............
  aaaannnnooootttthhhheeeerrrr sssseeeeccccttttiiiioooonnnn hhhheeeeaaaaddddiiiinnnngggg

The lines that  begin  with  a  period  are  the  formatting

requests.   For  example, ....PPPPPPPP calls for starting a new para-

graph.  The precise meaning of ....PPPPPPPP depends  on  what  output

device is being used (typesetter or terminal, for instance),

and on what publication the document will  appear  in.   For

example,  ----mmmmssss  normally assumes that a paragraph is preceded

by a space (one line in nnnnrrrrooooffffffff, 1/2 line in ttttrrrrooooffffffff),  and  the

first  word  is indented.  These rules can be changed if you

like, but they are changed by changing the interpretation of

....PPPPPPPP, not by re-typing the document.

  To actually produce a document in  standard  format  using

----mmmmssss, use the command

  ttttrrrrooooffffffff ----mmmmssss ffffiiiilllleeeessss ............

for the typesetter, and

  nnnnrrrrooooffffffff ----mmmmssss ffffiiiilllleeeessss ............

                     November 16, 1985

36                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

for a terminal.  The ----mmmmssss argument tells ttttrrrrooooffffffff and  nnnnrrrrooooffffffff  to

use the manuscript package of formatting requests.

  There are several similar packages;  check  with  a  local

expert  to  determine  which  ones are in common use on your


_S_u_p_p_o_r_t_i_n_g _T_o_o_l_s

  In addition to the basic formatters, there is  a  host  of

supporting  programs  that  help  with document preparation.

The list in the next few paragraphs is far from complete, so

browse  through  the manual and check with people around you

for other possibilities.

  eeeeqqqqnnnn and nnnneeeeqqqqnnnn let you integrate mathematics into  the  text

of  a  document,  in  an easy-to-learn language that closely

resembles the way you would speak it  aloud.   For  example,

the eeeeqqqqnnnn input

  ssssuuuummmm ffffrrrroooommmm iiii====0000 ttttoooo nnnn xxxx ssssuuuubbbb iiii ~~~~====~~~~ ppppiiii oooovvvveeeerrrr 2222

produces the output

999                         _i_=078_R78_n999 _x_i _=99 278_J9__

  The program ttttbbbbllll provides an analogous service for  prepar-

ing tabular material; it does all the computations necessary

to  align  complicated  columns  with  elements  of  varying


                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        37

  rrrreeeeffffeeeerrrr prepares bibliographic citations from a  data  base,

in  whatever style is defined by the formatting package.  It

looks after all  the  details  of  numbering  references  in

sequence,  filling  in  page and volume numbers, getting the

author's initials and the journal name right, and so on.

  ssssppppeeeellllllll and ttttyyyyppppoooo detect  possible  spelling  mistakes  in  a

document.   ssssppppeeeellllllll works by comparing the words in your docu-

ment to a dictionary, printing those that  are  not  in  the

dictionary.   It  knows  enough  about  English  spelling to

detect plurals and the like, so it does  a  very  good  job.

ttttyyyyppppoooo  looks  for  words  which  are  ``unusual'', and prints

those.  Spelling mistakes tend to be more unusual, and  thus

show up early when the most unusual words are printed first.

  ggggrrrreeeepppp looks through a set of files for lines that contain a

particular  text  pattern  (rather like the editor's context

search does, but on a bunch of files).  For example,

  ggggrrrreeeepppp ''''iiiinnnngggg$$$$'''' cccchhhhaaaapppp****

will find all lines that end with the  letters  iiiinnnngggg  in  the

files  cccchhhhaaaapppp****.   (It  is almost always a good practice to put

single quotes around the pattern you're  searching  for,  in

case  it contains characters like **** or $$$$ that have a special

meaning to the shell.) ggggrrrreeeepppp is often useful for finding  out

in  which of a set of files the misspelled words detected by

ssssppppeeeellllllll are actually located.

  ddddiiiiffffffff prints a list of the differences between  two  files,

                     November 16, 1985

38                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

so  you  can compare two versions of something automatically

(which certainly beats proofreading by hand).

  wwwwcccc counts the words, lines and  characters  in  a  set  of

files.   ttttrrrr translates characters into other characters; for

example it will convert upper to lower case and vice  versa.

This translates upper into lower:

  ttttrrrr AAAA----ZZZZ aaaa----zzzz <<<<iiiinnnnppppuuuutttt >>>>oooouuuuttttppppuuuutttt

  ssssoooorrrrtttt sorts files in a variety of ways; ccccrrrreeeeffff  makes  cross-

references;  ppppttttxxxx  makes a permuted index (keyword-in-context

listing).  sssseeeedddd provides many of the  editing  facilities  of

eeeedddd, but can apply them to arbitrarily long inputs.  aaaawwwwkkkk pro-

vides the ability to do both pattern  matching  and  numeric

computations,  and  to  conveniently  process  fields within

lines.  These programs are for more advanced users, and they

are  not  limited to document preparation.  Put them on your

list of things to learn about.

  Most of these programs are either independently documented

(like  eeeeqqqqnnnn  and  ttttbbbbllll),  or  are sufficiently simple that the

description in the  _U_N_I_X  _P_r_o_g_r_a_m_m_e_r'_s  _M_a_n_u_a_l  is  adequate


_H_i_n_t_s _f_o_r _P_r_e_p_a_r_i_n_g _D_o_c_u_m_e_n_t_s

  Most documents go through several  versions  (always  more

than   you  expected)  before  they  are  finally  finished.

Accordingly, you should do whatever possible to make the job

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        39

of changing them easy.

  First, when you do the  purely  mechanical  operations  of

typing, type so that subsequent editing will be easy.  Start

each sentence on a new line.  Make lines  short,  and  break

lines  at  natural  places,  such  as after commas and semi-

colons, rather than  randomly.   Since  most  people  change

documents  by  rewriting  phrases  and  adding, deleting and

rearranging sentences, these precautions simplify any  edit-

ing you have to do later.

  Keep the individual files of a  document  down  to  modest

size,  perhaps  ten  to fifteen thousand characters.  Larger

files edit more slowly, and of course if  you  make  a  dumb

mistake  it's  better  to have clobbered a small file than a

big one.  Split into files  at  natural  boundaries  in  the

document,  for the same reasons that you start each sentence

on a new line.

  The second aspect of making change easy is to  not  commit

yourself to formatting details too early.  One of the advan-

tages of formatting packages like ----mmmmssss is  that  they  permit

you to delay decisions to the last possible moment.  Indeed,

until a document is printed, it is not even decided  whether

it will be typeset or put on a line printer.

  As a rule of thumb, for all but the most trivial jobs, you

should  type  a  document in terms of a set of requests like

....PPPPPPPP, and then define them appropriately, either by using one

                     November 16, 1985

40                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

of  the canned packages (the better way) or by defining your

own nnnnrrrrooooffffffff and ttttrrrrooooffffffff commands.  As long as you  have  entered

the text in some systematic way, it can always be cleaned up

and re-formatted by a judicious combination of editing  com-

mands and request definitions.

_I_V.  _P_R_O_G_R_A_M_M_I_N_G

  There will be no attempt made to teach any of the program-

ming  languages  available  but a few words of advice are in

order.  One of the reasons why the UNIX system is a  produc-

tive programming environment is that there is already a rich

set of tools  available,  and  facilities  like  pipes,  I/O

redirection, and the capabilities of the shell often make it

possible to do a  job  by  pasting  together  programs  that

already exist instead of writing from scratch.

_T_h_e _S_h_e_l_l

  The pipe mechanism lets you  fabricate  quite  complicated

operations out of spare parts that already exist.  For exam-

ple, the first draft of the ssssppppeeeellllllll program was (roughly)

  ccccaaaatttt ............     _c_o_l_l_e_c_t _t_h_e _f_i_l_e_s
  |||| ttttrrrr ............    _p_u_t _e_a_c_h _w_o_r_d _o_n _a _n_e_w _l_i_n_e
  |||| ttttrrrr ............    _d_e_l_e_t_e _p_u_n_c_t_u_a_t_i_o_n, _e_t_c.
  |||| ssssoooorrrrtttt      _i_n_t_o _d_i_c_t_i_o_n_a_r_y _o_r_d_e_r
  |||| uuuunnnniiiiqqqq      _d_i_s_c_a_r_d _d_u_p_l_i_c_a_t_e_s
  |||| ccccoooommmmmmmm      _p_r_i_n_t _w_o_r_d_s _i_n _t_e_x_t
          _b_u_t _n_o_t _i_n _d_i_c_t_i_o_n_a_r_y

More pieces have been added subsequently, but  this  goes  a

long way for such a small effort.

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        41

  The editor can be made to do things  that  would  normally

require  special programs on other systems.  For example, to

list the first and last lines of each of  a  set  of  files,

such as a book, you could laboriously type

  eeee cccchhhhaaaapppp1111....1111
  eeee cccchhhhaaaapppp1111....2222

But you can do the job much more easily.  One way is to type

  llllssss cccchhhhaaaapppp**** >>>>tttteeeemmmmpppp

to get the list of filenames into a file.   Then  edit  this

file to make the necessary series of editing commands (using

the global commands of eeeedddd), and write it into  ssssccccrrrriiiipppptttt.   Now

the command

  eeeedddd <<<<ssssccccrrrriiiipppptttt

will produce the same output as the laborious  hand  typing.

Alternately (and more easily), you can use the fact that the

shell will perform loops, repeating a set of  commands  over

and over again for a set of arguments:

  ffffoooorrrr iiii iiiinnnn cccchhhhaaaapppp****
       eeeedddd $$$$iiii <<<<ssssccccrrrriiiipppptttt

This sets the shell variable iiii to each file  name  in  turn,

then  does  the  command.   You can type this command at the

terminal, or put it in a file for later execution.

                     November 16, 1985

42                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

_P_r_o_g_r_a_m_m_i_n_g _t_h_e _S_h_e_l_l

  An option often overlooked by newcomers is that the  shell

is  itself  a  programming language, with variables, control

flow (iiiiffff----eeeellllsssseeee, wwwwhhhhiiiilllleeee, ffffoooorrrr, ccccaaaasssseeee), subroutines, and interrupt

handling.  Since there are many building-block programs, you

can sometimes avoid writing a new program merely by  piecing

together  some  of  the  building  blocks with shell command


  We will not go into any details here; examples  and  rules

can  be found in _A_n _I_n_t_r_o_d_u_c_t_i_o_n _t_o _t_h_e _U_N_I_X _S_h_e_l_l, by S. R.


_P_r_o_g_r_a_m_m_i_n_g _i_n _C

  If you are undertaking anything substantial, C is the only

reasonable choice of programming language: everything in the

UNIX system is tuned to it.  The system itself is written in

C, as are most of the programs that run on it.  It is also a

easy language to use once you get started.  C is  introduced

and  fully  described in _T_h_e _C _P_r_o_g_r_a_m_m_i_n_g _L_a_n_g_u_a_g_e by B. W.

Kernighan and D. M. Ritchie (Prentice-Hall, 1978).   Several

sections  of the manual describe the system interfaces, that

is, how you do I/O and similar functions.   Read  _U_N_I_X  _P_r_o_-

_g_r_a_m_m_i_n_g for more complicated things.

  Most input and output in C is best handled with the  stan-

dard I/O library, which provides a set of I/O functions that

exist in compatible  form  on  most  machines  that  have  C

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        43

compilers.   In  general,  it's wisest to confine the system

interactions in a program to the facilities provided by this


  C programs that don't depend too much on special  features

of UNIX (such as pipes) can be moved to other computers that

have C compilers.  The list of such machines grows daily; in

addition  to  the  original PDP-11, it currently includes at

least Honeywell 6000, IBM 370, Interdata 8/32, Data  General

Nova  and  Eclipse,  HP 2100, Harris /7, VAX 11/780, SEL 86,

and Zilog Z80.  Calls to the standard I/O library will  work

on all of these machines.

  There are a number of supporting programs that go with  C.

lllliiiinnnntttt  checks  C programs for potential portability problems,

and detects errors such as  mismatched  argument  types  and

uninitialized variables.

  For larger programs (anything whose source is on more than

one  file) mmmmaaaakkkkeeee allows you to specify the dependencies among

the source files and the processing steps needed to  make  a

new  version;  it then checks the times that the pieces were

last changed and does the minimal amount of  recompiling  to

create a consistent updated version.

  The debugger aaaaddddbbbb is useful for digging  through  the  dead

bodies  of  C  programs,  but is rather hard to learn to use

effectively.  The most effective  debugging  tool  is  still

careful  thought,  coupled  with  judiciously  placed  print

                     November 16, 1985

44                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s


  The C compiler provides a limited instrumentation service,

so you can find out where programs spend their time and what

parts are worth optimizing.  Compile the routines  with  the

----pppp  option;  after the test run, use pppprrrrooooffff to print an execu-

tion profile.  The command ttttiiiimmmmeeee  will  give  you  the  gross

run-time  statistics  of  a  program, but they are not super

accurate or reproducible.

_O_t_h_e_r _L_a_n_g_u_a_g_e_s

  If you _h_a_v_e to use Fortran, there are  two  possibilities.

You  might  consider Ratfor, which gives you the decent con-

trol structures and free-form input that characterize C, yet

lets you write code that is still portable to other environ-

ments.  Bear in mind that  UNIX  Fortran  tends  to  produce

large  and  relatively  slow-running programs.  Furthermore,

supporting software like aaaaddddbbbb, pppprrrrooooffff, etc., are all  virtually

useless  with Fortran programs.  There may also be a Fortran

77 compiler on your system.  If so, this is a viable  alter-

native  to Ratfor, and has the non-trivial advantage that it

is compatible with C and related programs.  (The Ratfor pro-

cessor and C tools can be used with Fortran 77 too.)

  If your application requires you to translate  a  language

into a set of actions or another language, you are in effect

building a compiler, though probably a small one.   In  that

case,  you should be using the yyyyaaaacccccccc compiler-compiler, which

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        45

helps you develop  a  compiler  quickly.   The  lllleeeexxxx  lexical

analyzer  generator  does  the  same  job  for  the  simpler

languages that can be expressed as regular expressions.   It

can be used by itself, or as a front end to recognize inputs

for a yyyyaaaacccccccc-based program.  Both yyyyaaaacccccccc and  lllleeeexxxx  require  some

sophistication  to  use,  but the initial effort of learning

them can be repaid many times over in programs that are easy

to change later on.

  Most UNIX systems also  make  available  other  languages,

such  as  Algol  68,  APL,  Basic, Lisp, Pascal, and Snobol.

Whether these  are  useful  depends  largely  on  the  local

environment:  if  someone  cares  about the language and has

worked on it, it may be in good shape.  If not, the odds are

strong that it will be more trouble than it's worth.

_V.  _U_N_I_X _R_E_A_D_I_N_G _L_I_S_T


K. L. Thompson and D.  M.  Ritchie,  _T_h_e  _U_N_I_X  _P_r_o_g_r_a_m_m_e_r'_s

_M_a_n_u_a_l,  Bell  Laboratories,  1978.   Lists commands, system

routines and interfaces,  file  formats,  and  some  of  the

maintenance   procedures.   You  can't  live  without  this,

although you will probably only need to read section 1.

_D_o_c_u_m_e_n_t_s _f_o_r _U_s_e _w_i_t_h _t_h_e _U_N_I_X _T_i_m_e-_s_h_a_r_i_n_g _S_y_s_t_e_m.  Volume

2  of the Programmer's Manual.  This contains more extensive

descriptions of major commands, and tutorials and  reference

manuals.   All  of the papers listed below are in it, as are

                     November 16, 1985

46                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

descriptions of most of the programs mentioned above.

D. M. Ritchie and K. L. Thompson,  ``The  UNIX  Time-sharing

System,''  CACM,  July 1974.  An overview of the system, for

people interested in operating systems.   Worth  reading  by

anyone  who  programs.  Contains a remarkable number of one-

sentence observations on how to do things right.

The Bell System Technical Journal (BSTJ)  Special  Issue  on

UNIX,  July/August,  1978,  contains  many papers describing

recent developments, and some retrospective material.

The 2nd International  Conference  on  Software  Engineering

(October,  1976)  contains several papers describing the use

of the Programmer's Workbench (PWB) version of UNIX.

_D_o_c_u_m_e_n_t _P_r_e_p_a_r_a_t_i_o_n:

B. W. Kernighan, ``A Tutorial Introduction to the UNIX  Text

Editor''  and  ``Advanced  Editing  on  UNIX,'' Bell Labora-

tories, 1978.  Beginners need the introduction; the advanced

material will help you get the most out of the editor.

M. E. Lesk, ``Typing Documents on UNIX,'' Bell Laboratories,

1978.   Describes  the ----mmmmssss macro package, which isolates the

novice from the vagaries of nnnnrrrrooooffffffff and ttttrrrrooooffffffff, and takes  care

of  most  formatting  situations.   If this specific package

isn't available on your system, something  similar  probably

is.  The most likely alternative is the PWB/UNIX macro pack-

age ----mmmmmmmm; see your local guru if you use PWB/UNIX.

                     November 16, 1985

_U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s                                        47

B. W. Kernighan and L. L. Cherry, ``A System for Typesetting

Mathematics,''  Bell  Laboratories  Computing  Science Tech.

Rep. 17.

M. E. Lesk, ``Tbl -  A  Program  to  Format  Tables,''  Bell

Laboratories CSTR 49, 1976.

J. F. Ossanna,  Jr.,  ``NROFF/TROFF  User's  Manual,''  Bell

Laboratories  CSTR  54,  1976.  ttttrrrrooooffffffff is the basic formatter

used  by  ----mmmmssss,  eeeeqqqqnnnn  and  ttttbbbbllll.   The  reference  manual   is

indispensable if you are going to write or maintain these or

similar programs.  But start with:

B. W. Kernighan, ``A TROFF  Tutorial,''  Bell  Laboratories,

1976.  An attempt to unravel the intricacies of ttttrrrrooooffffffff.


B. W.  Kernighan  and  D.  M.  Ritchie,  _T_h_e  _C  _P_r_o_g_r_a_m_m_i_n_g

_L_a_n_g_u_a_g_e,  Prentice-Hall,  1978.  Contains a tutorial intro-

duction, complete discussions of all language features,  and

the reference manual.

B. W. Kernighan and D.  M.  Ritchie,  ``UNIX  Programming,''

Bell  Laboratories,  1978.   Describes how to interface with

the system from C programs: I/O calls, signals, processes.

S. R. Bourne, ``An Introduction to the  UNIX  Shell,''  Bell

Laboratories,  1978.   An  introduction and reference manual

for the Version 7 shell.  Mandatory reading if you intend to

make effective use of the programming power of this shell.

                     November 16, 1985

48                                        _U_N_I_X _f_o_r _B_e_g_i_n_n_e_r_s

S. C. Johnson, ``Yacc  -  Yet  Another  Compiler-Compiler,''

Bell Laboratories CSTR 32, 1978.

M. E. Lesk, ``Lex - A  Lexical  Analyzer  Generator,''  Bell

Laboratories CSTR 39, 1975.

S. C. Johnson, ``Lint, a C Program Checker,''  Bell  Labora-

tories CSTR 65, 1977.

S. I. Feldman, ``MAKE - A Program for  Maintaining  Computer

Programs,'' Bell Laboratories CSTR 57, 1977.

J. F. Maranzano and S. R. Bourne, ``A Tutorial  Introduction

to  ADB,'' Bell Laboratories CSTR 62, 1977.  An introduction

to a powerful but complex debugging tool.

S. I. Feldman and P. J. Weinberger, ``A Portable Fortran  77

Compiler,''  Bell Laboratories, 1978.  A full Fortran 77 for

UNIX systems.

_M_a_y _1_9_7_9

                     November 16, 1985

                   D O C U M E N T A T I O N   M E N U
This menu allows you to access documents about some of the
features of UNIX and this system in general.  Many of the
documents are very long. WARNING - Once the listing starts,
it will not STOP until the whole document has been listed. 
It is recommended that you 'download' the document entitled
BEGIN and study it for a general background of the system.

     Size in bytes      Name of Document
     -------------- -----------------
A    55330              ADVICE.doc 
B    81391              BEGIN.doc 
C   143449              CSH.doc 
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E    76644              SETUP.doc 
F    73228              SHELL.doc 
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H    68271              UNIX.doc 
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