Re: OT: Which tool, and how, to get partial string from file?

From: Miquel van Smoorenburg (miquels_at_cistron.nl)
Date: 08/21/04

  • Next message: Hans Oluf Hagen: "Re: Evolution in Norwegian?" 
    Date: Sat, 21 Aug 2004 12:36:48 +0000 (UTC)
To: debian-user@lists.debian.org

    In article <412699A2.8030407@acu.edu>,
    Kent West <westk@acu.edu> wrote:
    >Miquel van Smoorenburg wrote:
    >
    >>In article <41265EB6.2050202@acu.edu>,
    >>Kent West <westk@acu.edu> wrote:
    >>
    >>
    >>>A programmer would know this . . , but not me ;-)
    >>>
    >>>I'm using a script to build a file by concatenating portions of two
    >>>other files. Then end result needs to be checked to make sure a certain
    >>>word shows up in a line.
    >>>
    >>>I know that "grep programm <this email message>" would return the line:
    >>>
    >>>A programmer would know this . . , but not me ;-)
    >>>
    >>>but what I want returned is just the word "programmer".
    >>>
    >>>
    >>
    >>sed -ne 's/^.*\(word_here\).*$/\1/p' < file
    >>
    >>
    >Here's my test script:
    >
    >> #!/bin/bash
    >>
    >> if [ sed -ne 's/^.*\(icewm\).*$/\1/p' < /home.local/snert/.xinitrc ] ;
    >> then
    >> echo "Yep"
    >> else
    >> echo "Nope"
    >> fi

    That's the complete wrong way to use '[' !

    You want something like:

    WORD=`sed -ne 's/^.*\(icewm\).*$/\1/p' < /home.local/snert/.xinitrc`
    if [ -n "$WORD" ]
    then
            ....

    For a primer on how to use '[', do "man test".

    >>BTW, why not simply
    >>
    >> if grep -q word file
    >> then
    >> # word was present in file
    >> bla
    >> bla
    >> fi
    >>
    >>
    >>
    >My test script:
    >
    >> #!/bin/bash
    >>
    >> if [ `grep -q icewm /home.local/snert/.xinitrc` ] ; then
    >> echo "Yep"

    I wrote

            if grep -q word file

    Why change it to

            if [ `grep -q icewm /home.local/snert/.xinitrc` ]

    ? That means something completely different.

    "sh" scripts are a programming language. They do what you say,
    not what you mean ;)

    After 'if' comes a command. The exit status of the command is used
    as return value: 0 is true, 1 (or any non-zero value) is false.
    The '[' thing is just a command. Look:

    $ ls -l /usr/bin/[
    -rwxr-xr-x 1 root root 23928 Jul 16 13:37 /usr/bin/[*

    It's also known as 'test'. See "man test".

    But you can put other commands there, like grep. "grep -q" exits
    with exit-status 0 (true) on a match. So that's why I said

            if grep -q word file

    and that's why it's completely different from if [ grep ...

    Mike. 

    -- 
The question is, what is a "manamanap".
The question is, who cares ?
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  • Next message: Hans Oluf Hagen: "Re: Evolution in Norwegian?"

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