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Full Discussion: Validating IP address.
Top Forums Shell Programming and Scripting Validating IP address. Post 302217147 by era on Tuesday 22nd of July 2008 04:05:24 AM
Old 07-22-2008
As a stylistic issue, I would dissuade from the use of grep -c and [ xxx -eq 0 ] -- especially on $? -- in favor of something like

Code:
if ! echo "$ipadd" | grep -E '...' >/dev/null; then
  echo -e "*** Bad ..." >&2
  exit 2
fi

Also note the redirection of the error message to file descriptor 2. You might want to add $0 to the beginning of the error message as well.

The use of {1} in the regular expression is obviously redundant. In order to reduce backtracking, you might want to use [01][0-9]{0,2} to cover all strings beginning with 0 or 1 in one go, aand adjust the subsequent expression accordingly.
 

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LEARN ABOUT MINIX

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)
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