If Then ElseIf Script - Confusion Around Expression's Syntax Post: 302554885

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Top Forums UNIX for Dummies Questions & Answers If Then ElseIf Script - Confusion Around Expression's Syntax Post 302554885 by zaxxon on Tuesday 13th of September 2011 09:37:11 AM

09-13-2011

Registered User

The elif-part doesn't make sense, because when the file has size 0 it can't have any content to be found by grep, as !s means the opposite, ie. <=0.

If you want to issue a command inside a test, you coud try like this:

Code:

if [[ -s /etc/passwd && $(head -1 /etc/passwd| grep -q root > /dev/null 2>&1; echo $?) == 0 ]]; then
    echo yo
else
    echo no
fi

... or as a separate sub if/then/fi below the check if the file exists and has a size >0.

To grep for more than one pattern as a logic "OR", you can use this:

Code:

grep -E "^Tick_Num|^Line_No" infile

The ^ tells it that it is the start of a line, ie. 1st character to follow and the pipe | separates the patterns.
A * would be writtens as .* in Regular Expressions and this would make no sense, as this could be everything and sowith always be true.

Another hint is to declare a variable, that contains the file name, since it is awful to type it over and over and when you want to change it, you change it at just 1 place.

Edit:
If "Tick_Num,Line_No,*" is a complete pattern, forget the lines above about grep -E

Last edited by zaxxon; 09-13-2011 at 10:50 AM.. Reason: added note

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zgrep

ZGREP(1)						      General Commands Manual							  ZGREP(1)

NAME

       zgrep - search possibly compressed files for a regular expression

SYNOPSIS

       zgrep [ grep_options ] [ -e ] pattern filename...

DESCRIPTION

       Zgrep  invokes  grep  on  compressed  or  gzipped  files.   These  grep	options  will  cause  zgrep  to  terminate  with  an  error  code:
       (-[drRzZ]|--di*|--exc*|--inc*|--rec*|--nu*).  All other options specified are passed directly to grep.  If no file is specified,  then  the
       standard input is decompressed if necessary and fed to grep.  Otherwise the given files are uncompressed if necessary and fed to grep.

       If the GREP environment variable is set, zgrep uses it as the grep program to be invoked.

EXIT CODE

       2 - An option that is not supported was specified.

AUTHOR

       Charles Levert (charles@comm.polymtl.ca)

SEE ALSO

       grep(1), gzexe(1), gzip(1), zdiff(1), zforce(1), zmore(1), znew(1)

																	  ZGREP(1)