[SWLUG] grep question

[Dave Lukes]

My 2p worth ...

	#!/bin/sh


	barf() { stat=$1; shift; echo "$*" >&2; exit $stat; }

	pause=

	if [ $# -lt 2 ]
	then    barf 1 "$0: usage: $0 [-p] pattern-file file ..."
	fi

	if [ "$1" = '-p' ]
	then    shift
		pause=yes
	fi

	patternfile="$1"
	shift

	if [ ! -r "$patternfile" ]
	then    barf 2 "$0: $patternfile isn't readable"
	fi

	while read pattern
	do      echo pattern \"$pattern\" matches ...
		grep "$pattern" "$@"
		case "$?" in
		0)	# OK
			;;
		1)	# no match
			echo "no matches"
			continue	# no need to pause ...
			;;
		*)	# something else wrong ...
			barf $? "grep problem ..."
		esac
		if [ "$pause" ]
		then    echo "Press <Enter> to continue"
			read junk
		fi
	done < "$patternfile"

which doesn't involve all the rereading the pattern file every time etc.,
and works for multiple files to be searched and stops if grep dies
for strange reasons (bogus patterns etc.)

For extra brownie points,
indent the grep output to make it more readable and/or
make the error messages more visible and/or
count the matches!!

Cheers,
	Dave.

On Tue, Feb 12, 2002 at 10:13:11AM +0000, bascule wrote:
> following some advice from telsa at the weekend i have answered my own 
> question by knocking up a script to do what i want...
> ...except that that's a lie, it took me ages! :-)
> i've pasted the scrpt below, there are some obvious flaws, there is no way to 
> pass arguments to the internal grep command (without altering the actual 
> script) and no means to show a screenfull at a time, i'd welcome comments, 
> esp. if i've missed some obvious and easier way of doing something, 
> 
> On Friday 08 February 2002 10:22 pm, you wrote:
> > if i am feeding a file to grep that has an expression on each line to
> > search through another file for matches, is there a way to output the line
> > of the file that has the matching expression as well as the match, or to
> > specify which line of the file to use as an expression?
> 
> --------begin--------
> #!/bin/bash
> # bgrep (bascule's grep)
> # this script feeds a file with patterns to grep and returns (if exists) both 
> a
>  match from
> # a second file and the pattern that matches it
> # Usage: bgrep [-p] PATTERN_FILE FILE
> # Search for matching expressions from file PATTERN_FILE that occur in file 
> FILE
> #
> # Options:
> #  -p: pause between each set of matches that is found
> #
> if [ $# -eq 2 ] && [ -f $1 ] && [ -f $2 ]
> 	then
> 	PATTERN_FILE=$1
> 	FILE=$2
> 	args=0
> elif [ $# -eq 3 ] && [ $1 = -p ] && [ -f $2 ] && [ -f $3 ]
> 	then
> 	PATTERN_FILE=$2
> 	FILE=$3
> 	args=0
> else
> 	args=1
> fi
> 
> case $args in
> 
> 	0)
> lines=`wc -l $PATTERN_FILE|gawk '{print $1}'`
> let flag=1
> while [ "$flag" -le "$lines" ]
> 	do
> 	echo "The pattern: `echo $(head -$flag $PATTERN_FILE|tail -1)`"
> 	echo "         matches..."
> 	grep "`echo $(head -$flag $PATTERN_FILE|tail -1)`" $FILE
> 		if [ $? = 1 ]
> 		then
> 		echo "    no matches found "
> 		elif [ $1 = -p ]
> 		then
> 		echo "Press <Enter> to continue"
> 		read input
> 		fi
> 	let flag="$flag + 1"
> done
> ;;
> 
> 	1)
> echo "Usage: bgrep [-p] PATTERN_FILE FILE"
> echo "Search for matching expressions from file PATTERN_FILE that occur in 
> file
>  FILE"
> echo ""
> echo "Options:"
> echo "  -p: pause between each set of matches that is found"
> echo ""
> exit
> ;;
> esac
> ---------end--------------
> 
> bascule
> 
> -- 
> Someone's behind this. Someone wants to see a war. [...] I've got to remember 
> that. This isn't a war. This is a crime.
> (Jingo)
> 
> _______________________________________________
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> http://swlug.org.uk/mailman/listinfo/discuss

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