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Full Discussion: Regular Expressions
Top Forums UNIX for Advanced & Expert Users Regular Expressions Post 302195669 by ramky79 on Thursday 15th of May 2008 04:55:55 PM
Old 05-15-2008
Regular Expressions
Hi,
below is a piece of code written by my predecessor at work.
I'm kind of a newbie and am trying to figure out all the regular expressions in this piece of code.
It is really a tough time for me to figure out all the regular expressions.

Please shed some light on the regular expressions in this code

ssh_list() {
typeset userAtHost="$1"
typeset dir="${2-.}"
typeset wild="${3-*}"

info "SSH list: $userAtHost $src $dst"

if [ "$REGION" != prod ] ;then
userAtHost=$LOGNAME@localhost
fi

# Save, disable, and restore the verbose flag - any
# verbose output would look like errors.
typeset verbose="$(set -o |sed -n 's/^verbose *//p')"
set +v
typeset msgs="$(sftp $userAtHost 2>&1 <<EOF
cd $dir
ls
EOF)"
if [ "$verbose" = on ] ;then
set -v
fi

# Strip the "Connecting to host..." line, prompts, blank lines
# and login banners. What's left should only be error messages.
typeset errs="$(echo "$msgs" |
sed -e '/^Connecting to .*\.\.\.$/d' \
-e 's/sftp > //g' \
-e '/^[ ]*$/d' \
-e '/^#/d' \
-e '/^[-dDlbcps][-rwxsStTlL]\{9\}+\{0,1\} /d')"

if [ "$errs" != "" ] ;then
error "$errs"
return 1
fi

echo "$msgs" |
while read line
do
case "$line" in -*\ $wild)
echo ${line##* }
;;esac
done

return 0
}

I'd like some explanation of these lines.... gurus please shed some light.

Thank you for your time.
Ram
 

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LEARN ABOUT BSD

re_comp

REGEX(3)						     Library Functions Manual							  REGEX(3)

NAME

       re_comp, re_exec - regular expression handler

SYNOPSIS

       char *re_comp(s)
       char *s;

       re_exec(s)
       char *s;

DESCRIPTION

       Re_comp	compiles a string into an internal form suitable for pattern matching.	Re_exec checks the argument string against the last string
       passed to re_comp.

       Re_comp returns 0 if the string s was compiled successfully; otherwise a string containing an error message  is	returned.  If  re_comp	is
       passed 0 or a null string, it returns without changing the currently compiled regular expression.

       Re_exec returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled regular
       expression, and -1 if the compiled regular expression was invalid (indicating an internal error).

       The strings passed to both re_comp and re_exec may have trailing or embedded newline characters; they are terminated by nulls.  The regular
       expressions recognized are described in the manual entry for ed(1), given the above difference.

SEE ALSO

       ed(1), ex(1), egrep(1), fgrep(1), grep(1)

DIAGNOSTICS

       Re_exec returns -1 for an internal error.

       Re_comp returns one of the following strings if an error occurs:

	    No previous regular expression,
	    Regular expression too long,
	    unmatched (,
	    missing ],
	    too many () pairs,
	    unmatched ).

3rd Berkeley Distribution					   May 15, 1985 							  REGEX(3)
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