Internet Surfer 2.0/Internet Surfer 2.0 (Wayzata Technology) (1996).iso/pc/text/mac/faqs.535

Text File | 1996-02-12 | 28KB | 682 lines

Frequently Asked Questions (FAQS);faqs.535



      2.1)  How do I remove a file whose name begins with a "-" ?
      2.2)  How do I remove a file with funny characters in the filename ?
      2.3)  How do I get a recursive directory listing?
      2.4)  How do I get the current directory into my prompt?
      2.5)  How do I read characters from the terminal in a shell script?
      2.6)  How do I rename "*.foo" to "*.bar", or change file names
              to lowercase?
      2.7)  Why do I get [some strange error message] when I
              "rsh host command" ?
      2.8)  How do I {set an environment variable, change directory} inside a
              program or shell script and have that change affect my
              current shell?
      2.9)  How do I redirect stdout and stderr separately in csh?
      2.10) How do I tell inside .cshrc if I'm a login shell?
      2.11) How do I construct a shell glob-pattern that matches all files
            except "." and ".." ?
      2.12) How do I find the last argument in a Bourne shell script?
      2.13) What's wrong with having '.' in your $PATH ?

      3.1)  How do I find out the creation time of a file?
      3.2)  How do I use "rsh" without having the rsh hang around
              until the remote command has completed?
      3.3)  How do I truncate a file?
      3.4)  Why doesn't find's "{}" symbol do what I want?
      3.5)  How do I set the permissions on a symbolic link?
      3.6)  How do I "undelete" a file?
      3.7)  How can a process detect if it's running in the background?
      3.8)  Why doesn't redirecting a loop work as intended?  (Bourne shell)
      3.9)  How do I run 'passwd', 'ftp', 'telnet', 'tip' and other interactive
              programs from a shell script or in the background?
      3.10) How do I find out the process ID of a program with a particular
            name from inside a shell script or C program?
      3.11) How do I check the exit status of a remote command
            executed via "rsh" ?
      3.12) Is it possible to pass shell variable settings into an awk program?
      3.13) How do I get rid of zombie processes that persevere?
      3.14) How do I get lines from a pipe as they are written instead of
            only in larger blocks.

      4.1)  How do I read characters from a terminal without requiring the user
              to hit RETURN?
      4.2)  How do I check to see if there are characters to be read without
              actually reading?
      4.3)  How do I find the name of an open file?
      4.4)  How can an executing program determine its own pathname?
      4.5)  How do I use popen() to open a process for reading AND writing?
      4.6)  How do I sleep() in a C program for less than one second?
      4.7)  How can I get setuid shell scripts to work?
      4.8)  How can I find out which user or process has a file open or is using
            a particular file system (so that I can unmount it?)
      4.9)  How do I keep track of people who are fingering me?
      4.10) Is it possible to reconnect a process to a terminal after it has
            been disconnected, e.g. after starting a program in the background
            and logging out?
      4.11) Is it possible to "spy" on a terminal, displaying the output
            that's appearing on it on another terminal?

      5.1)  Can shells be classified into categories?
      5.2)  How do I "include" one shell script from within another
            shell script?
      5.3)  Do all shells have aliases?  Is there something else that
            can be used?
      5.4)  How are shell variables assigned?
      5.5)  How can I tell if I am running an interactive shell?
      5.6)  What "dot" files do the various shells use?
      5.7)  I would like to know more about the differences between the
            various shells.  Is this information available some place?

      6.1)  Disclaimer and introduction.
      6.2)  A very brief look at Unix history.
      6.3)  Main Unix flavors.
      6.4)  Unix Standards.
      6.5)  Identifying your Unix flavor.
      6.6)  Brief notes on some well-known (commercial/PD) Unices.
      6.7)  Real-time Unices.
      6.8)  Unix glossary.
      6.9)  Acknowledgements.

      7.1)  RCS vs SCCS:  Introduction
      7.2)  RCS vs SCCS:  How do the interfaces compare?
      7.3)  RCS vs SCCS:  What's in a Revision File?
      7.4)  RCS vs SCCS:  What are the keywords?
      7.5)  What's an RCS symbolic name?
      7.6)  RCS vs SCCS:  How do they compare for performance?
      7.7)  RCS vs SCCS:  Version Identification.
      7.8)  RCS vs SCCS:  How do they handle with problems?
      7.9)  RCS vs SCCS:  Conversion.
      7.10) RCS vs SCCS:  Support
      7.11) RCS vs SCCS:  Command Comparison
      7.12) RCS vs SCCS:  Acknowledgements
      7.13) Can I get more information on configuration management systems?

      If you're looking for the answer to, say, question 2.5, look in
      part 2 and search for the regular expression "^2.5)".

While these are all legitimate questions, they seem to crop up in
comp.unix.questions or comp.unix.shell on an annual basis, usually
followed by plenty of replies (only some of which are correct) and then
a period of griping about how the same questions keep coming up.  You
may also like to read the monthly article "Answers to Frequently Asked
Questions" in the newsgroup "news.announce.newusers", which will tell
you what "UNIX" stands for.

With the variety of Unix systems in the world, it's hard to guarantee
that these answers will work everywhere.  Read your local manual pages
before trying anything suggested here.  If you have suggestions or
corrections for any of these answers, please send them to to
[e-mail].

--
Ted Timar - [e-mail]
Empress Software, 3100 Steeles Ave E, Markham, Ont., Canada L3R 8T3
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*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Frequently Asked Questions about Unix (index) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/contents
! Version: $Id: contents,v 2.0 92/10/20 12:06:12 tmatimar Exp $

  The following seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
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! Subject: Unix - Frequently Asked Questions (Contents) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/contents
! Version: $Id: contents,v 2.1 92/12/04 07:43:28 tmatimar Exp $

  The following seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
***************
*** 23,28 ****
--- 23,29 ----
         they already knew all of the answers.
        5.*) Questions pertaining to the various shells, and the differences.
        6.*) An overview of Unix variants.
+       7.*) An comparison of configuration management systems (RCS, SCCS).

  The following questions are answered:

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*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Frequently Asked Questions about Unix (1/7) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/part1
! Version: $Id: part1,v 2.0 92/10/20 12:06:59 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (1/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part1
! Version: $Id: part1,v 2.1 92/12/04 07:43:43 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
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*** 2,12 ****
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  Followup-To: comp.unix.questions
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  Approved: [e-mail]

! Archive-name: unix-faq/part2
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  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (2/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part2
! Version: $Id: part2,v 2.1 92/12/04 07:43:45 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
***************
*** 586,596 ****
        has already been redirected so only stderr actually winds up in
        stderr_file.

!       Sometimes it's easier to let sh do the work for you.

!     sh -c 'command >stdout_file 2>stderr_file'

  2.10) How do I tell inside .cshrc if I'm a login shell?

        When people ask this, they usually mean either

--- 586,600 ----
        has already been redirected so only stderr actually winds up in
        stderr_file.

!       If what you want is to avoid redirecting stdout at all, let sh
!       do it for you.

!     sh -c 'command 2>stderr_file'

  2.10) How do I tell inside .cshrc if I'm a login shell?
+
+       From: [e-mail] (Mark Brader)
+       Date: Mon, 26 Oct 1992 20:15:00 -0500

        When people ask this, they usually mean either

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*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Frequently Asked Questions about Unix (3/7) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/part3
! Version: $Id: part3,v 2.0 92/10/20 12:07:07 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (3/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part3
! Version: $Id: part3,v 2.1 92/12/04 07:43:49 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
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***************
*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Frequently Asked Questions about Unix (4/7) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/part4
! Version: $Id: part4,v 2.0 92/10/20 12:07:10 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (4/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part4
! Version: $Id: part4,v 2.1 92/12/04 07:43:53 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
***************
*** 438,443 ****
--- 438,447 ----

  4.9)  How do I keep track of people who are fingering me?

+       From: [e-mail] (Jonathan I. Kamens)
+       From: [e-mail] (Nikola Malenovic)
+       Date: Mon, 23 Nov 1992 16:01:45 -0600
+
        Generally, you can't find out the userid of someone who is
        fingering you from a remote machine.  You may be able to
        find out which machine the remote request is coming from.
***************
*** 466,481 ****
        For more information join the rfc931-users mailing list,
        [e-mail].

!       There are two caveats relating to this answer.  The first is that
!       many NFS systems won't allow the recognize the named pipe
!       correctly.  This means that trying to read the pipe on another
!       machine will either block until it times out, or see it as a
!       zero-length file, and never print it.

        The second problem is that on many systems, fingerd checks that
        the .plan file contains data (and is readable) before trying to
!       read it.  This will not cause remote fingers to miss your .plan
!       file entirely.

  4.10) Is it possible to reconnect a process to a terminal after it has
        been disconnected, e.g. after starting a program in the background
--- 470,493 ----
        For more information join the rfc931-users mailing list,
        [e-mail].

!       There are three caveats relating to this answer.  The first is
!       that many NFS systems won't recognize the named pipe correctly.
!       This means that trying to read the pipe on another machine will
!       either block until it times out, or see it as a zero-length file,
!       and never print it.

        The second problem is that on many systems, fingerd checks that
        the .plan file contains data (and is readable) before trying to
!       read it.  This will cause remote fingers to miss your .plan file
!       entirely.
!
!       The third problem is that a system that supports named pipes
!       usually has a fixed number of named pipes available on the
!       system at any given time - check the kernel config file and
!       FIFOCNT option.  If the number of pipes on the system exceeds the
!       FIFOCNT value, the system blocks new pipes until somebody frees
!       the resources.  The reason for this is that buffers are allocated
!       in a non-paged memory.

  4.10) Is it possible to reconnect a process to a terminal after it has
        been disconnected, e.g. after starting a program in the background
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*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Frequently Asked Questions about Unix (5/7) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/part5
! Version: $Id: part5,v 2.0 92/10/20 12:07:13 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (5/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part5
! Version: $Id: part5,v 2.1 92/12/04 07:43:55 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
***************
*** 87,93 ****
        Date: Wed, 7 Oct 92 14:28:18 -0500

        All of the major shells other than sh have aliases, but they
!       don't all work the same way.  For example, some don't except
        arguments.

        Although not strictly equivalent, shell functions (which exist in
--- 87,93 ----
        Date: Wed, 7 Oct 92 14:28:18 -0500

        All of the major shells other than sh have aliases, but they
!       don't all work the same way.  For example, some don't accept
        arguments.

        Although not strictly equivalent, shell functions (which exist in
***************
*** 113,127 ****
  5.5)  How can I tell if I am running an interactive shell?

        From: [e-mail] (Matthew Wicks)
!       Date: Wed, 7 Oct 92 14:28:18 -0500

!       In the Bourne shell category look for the variable $PROMPT.  In
!       the C shell category, look for the variable $prompt.

  5.6)  What "dot" files do the various shells use?

        From: [e-mail] (Matthew Wicks)
!       Date: Wed, 7 Oct 92 14:28:18 -0500

        Although this may not be a complete listing, this provides the
        majority of information.
--- 113,139 ----
  5.5)  How can I tell if I am running an interactive shell?

        From: [e-mail] (Matthew Wicks)
!       From: [e-mail] (DaviD W. Sanderson)
!       Date: Fri, 23 Oct 92 11:59:19 -0600

!       In the C shell category, look for the variable $prompt.

+       In the Bourne shell category, you can look for the variable $PS1,
+       however, it is better to check the variable $-.  If $- contains
+       an 'i', the shell is interactive.  Test like so:
+
+       case $- in
+       *i*)    # do things for interactive shell
+               ;;
+       *)      # do things for non-interactive shell
+               ;;
+       esac
+
  5.6)  What "dot" files do the various shells use?

        From: [e-mail] (Matthew Wicks)
!       From: [e-mail] (Thomas M. Breuel)
!       Date: Wed, 28 Oct 92 03:30:36 +0100

        Although this may not be a complete listing, this provides the
        majority of information.
***************
*** 178,184 ****
        Start-up (in this order):
                /etc/profile  - login shells.
                .bash_profile - login shells.
!               .bashrc       - interactive shells.

        Others:
                .inputrc      - Readline initialization.
--- 190,201 ----
        Start-up (in this order):
                /etc/profile  - login shells.
                .bash_profile - login shells.
!               .profile      - login if no .bash_profile is present.
!               .bashrc       - interactive non-login shells.
!               $ENV          - always, if it is set.
!
!       Upon termination:
!               .bash_logout  - login shells.

        Others:
                .inputrc      - Readline initialization.
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*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
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! Subject: Frequently Asked Questions about Unix (6/7) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/part6
! Version: $Id: part6,v 2.0 92/10/20 12:07:30 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (6/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part6
! Version: $Id: part6,v 2.1 92/12/04 07:43:57 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
*** /tmp/,RCSt1a18351    Fri Dec  4 07:46:45 1992
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***************
*** 2,12 ****
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Frequently Asked Questions about Unix (7/7) [Biweekly posting]
  Approved: [e-mail]

! Archive-name: unix-faq/part7
! Version: $Id: part7,v 2.0 92/10/20 12:07:46 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
--- 2,12 ----
  Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
  Followup-To: comp.unix.questions
  Organization: Empress Software
! Subject: Unix - Frequently Asked Questions (7/7) [Frequent posting]
  Approved: [e-mail]

! Archive-name: unix-faq/faq/part7
! Version: $Id: part7,v 2.1 92/12/04 07:44:00 tmatimar Exp $

  These seven articles contain the answers to some Frequently Asked
  Questions often seen in comp.unix.questions and comp.unix.shell.
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From: [e-mail] (Ted M A Timar)
Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
Subject: Unix - Frequently Asked Questions (1/7) [Frequent posting]
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Archive-name: unix-faq/faq/part1
Version: $Id: part1,v 2.1 92/12/04 07:43:43 tmatimar Exp $

These seven articles contain the answers to some Frequently Asked
Questions often seen in comp.unix.questions and comp.unix.shell.
Please don't ask these questions again, they've been answered plenty
of times already - and please don't flame someone just because they may
not have read this particular posting.  Thank you.

These articles are divided approximately as follows:

      1.*) General questions.
      2.*) Relatively basic questions, likely to be asked by beginners.
      3.*) Intermediate questions.
      4.*) Advanced questions, likely to be asked by people who thought
       they already knew all of the answers.
      5.*) Questions pertaining to the various shells, and the differences.
      6.*) An overview of Unix variants.
      7.*) An comparison of configuration management systems (RCS, SCCS).

This article includes answers to:

      1.1)  Who helped you put this list together?
      1.2)  When someone refers to 'rn(1)' or 'ctime(3)', what does
              the number in parentheses mean?
      1.3)  What does {some strange unix command name} stand for?
      1.4)  How does the gateway between "comp.unix.questions" and the
              "info-unix" mailing list work?
      1.5)  What are some useful Unix or C books?
      1.6)  What happened to the pronunciation list that used to be
              part of this document?

If you're looking for the answer to, say, question 1.5, and want to skip
everything else, you can search ahead for the regular expression "^1.5)".

While these are all legitimate questions, they seem to crop up in
comp.unix.questions or comp.unix.shell on an annual basis, usually
followed by plenty of replies (only some of which are correct) and then
a period of griping about how the same questions keep coming up.  You
may also like to read the monthly article "Answers to Frequently Asked
Questions" in the newsgroup "news.announce.newusers", which will tell
you what "UNIX" stands for.

With the variety of Unix systems in the world, it's hard to guarantee
that these answers will work everywhere.  Read your local manual pages
before trying anything suggested here.  If you have suggestions or
corrections for any of these answers, please send them to to
[e-mail].

1.1)  Who helped you put this list together?

      I took over the maintenance of this list.  Almost all of the work
      (and the credit) for generating this compilation was done by
      Steve Hayman.

      We also owe a great deal of thanks to dozens of Usenet readers who
      submitted questions, answers, corrections and suggestions for this
      list.  Special thanks go to Maarten Litmaath, Guy Harris and
      Jonathan Kamens, who have all made many especially valuable
      contributions.

      Part 5 of this document (shells) was written almost entirely by
      Matthew Wicks <[e-mail]>.

      Part 6 of this document (Unix flavours) was written almost entirely by
      Pierre (P.) Lewis <[e-mail]>.

      Where possible the author of each question and the date it was last
      updated is given at the top.  Unfortunately, I only started this
      practice recently, and much of the information is lost.  I was also
      negligent in keeping track of who provided updates to questions.
      Sorry to those who have made valuable contributions, but did not
      receive the credit and recognition that they legitimately deserve.

1.2)  When someone refers to 'rn(1)' or 'ctime(3)', what does
      the number in parentheses mean?

      It looks like some sort of function call, but it isn't.  These
      numbers refer to the section of the "Unix manual" where the
      appropriate documentation can be found.  You could type "man 3
      ctime" to look up the manual page for "ctime" in section 3 of
      the manual.

      The traditional manual sections are:

    1    User-level  commands
    2    System calls
    3    Library functions
    4    Devices and device drivers
    5    File formats
    6    Games
    7    Various miscellaneous stuff - macro packages etc.
    8    System maintenance and operation commands

      Some Unix versions use non-numeric section names.  For instance,
      Xenix uses "C" for commands and "S" for functions.

      Each section has an introduction, which you can read with "man #
      intro" where # is the section number.

      Sometimes the number is necessary to differentiate between a
      command and a library routine or system call of the same name.
      For instance, your system may have "time(1)", a manual page about
      the 'time' command for timing programs, and also "time(3)", a
      manual page about the 'time' subroutine for determining the
      current time.  You can use "man 1 time" or "man 3 time" to
      specify which "time" man page you're interested in.

      You'll often find other sections for local programs or even
      subsections of the sections above - Ultrix has sections 3m, 3n,
      3x and 3yp among others.

1.3)  What does {some strange unix command name} stand for?

      awk = "Aho Weinberger and Kernighan"

    This language was named by its authors, Al Aho, Peter
    Weinberger and Brian Kernighan.

      grep = "Global Regular Expression Print"

    grep comes from the ed command to print all lines matching a
    certain pattern

            g/re/p

    where "re" is a "regular expression".

      fgrep = "Fixed GREP".

    fgrep searches for fixed strings only.  The "f" does not stand
    for "fast" - in fact, "fgrep foobar *.c" is usually slower than
    "egrep foobar *.c"  (Yes, this is kind of surprising. Try it.)