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Full Discussion: Regular Expressions
Top Forums UNIX for Advanced & Expert Users Regular Expressions Post 302195825 by era on Friday 16th of May 2008 03:08:38 AM
Old 05-16-2008
Quote:
Originally Posted by ramky79
# 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
This one even has a comment to explain what it does. It disables verbose debugging (disables set -v if set), remembering the previous state of the flag in the verbose variable.

Quote:
# 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')"
Again, the comments are probably better than any detailed attempt at going through the individual regular expressions. Any "Connecting to ..." line is removed. Any sftp> prompt is removed. Any empty line is removed. Any line beginning with a hash sign is removed. The last one looks vaguely like it's intended to remove directory listing output.

Quote:
echo "$msgs" |
while read line
do
case "$line" in -*\ $wild)
echo ${line##* }
;;esac
done
This prints any line from $msgs which matches a dash, followed by anything, followed by a space, followed by the value of the variable $wild, with everything up to the last space trimmed away. (None of this involves any regular expressions, strictly speaking; both the case statement and the ${var##subst} interpolation work with glob patterns.)

$wild is defined up at the beginning of the function as either positional argument $3 or (if that is empty) an asterisk, which matches anything in glob wildcard notation.
 

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re_comp(3C)						   Standard C Library Functions 					       re_comp(3C)

NAME
re_comp, re_exec - compile and execute regular expressions SYNOPSIS
#include <re_comp.h> char *re_comp(const char *string); int re_exec(const char *string); DESCRIPTION
The re_comp() function converts a regular expression string (RE) into an internal form suitable for pattern matching. The re_exec() func- tion compares the string pointed to by the string argument with the last regular expression passed to re_comp(). If re_comp() is called with a null pointer argument, the current regular expression remains unchanged. Strings passed to both re_comp() and re_exec() must be terminated by a null byte, and may include NEWLINE characters. The re_comp() and re_exec() functions support simple regular expressions, which are defined on the regexp(5) manual page. The regular expressions of the form {m}, {m,}, or {m,n} are not supported. RETURN VALUES
The re_comp() function returns a null pointer when the string pointed to by the string argument is successfully converted. Otherwise, a pointer to one of the following error message strings is returned: No previous regular expression Regular expression too long unmatched ( missing ] too many () pairs unmatched ) Upon successful completion, re_exec() returns 1 if string matches the last compiled regular expression. Otherwise, re_exec() returns 0 if string fails to match the last compiled regular expression, and -1 if the compiled regular expression is invalid (indicating an internal error). ERRORS
No errors are defined. USAGE
For portability to implementations conforming to X/Open standards prior to SUS, regcomp(3C) and regexec(3C) are preferred to these func- tions. See standards(5). SEE ALSO
grep(1), regcmp(1), regcmp(3C), regcomp(3C), regexec(3C), regexpr(3GEN), regexp(5), standards(5) SunOS 5.11 26 Feb 1997 re_comp(3C)
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