# grep -l <string> <filenames> | xargs sed -i 's/<string>/<replacement>/'

How this works

Option -l (that’s not the number, but the lower-case letter) causes filenames to be output that contain <string>. xargs takes these and feeds them one at a time to sed which replaces the first occurrance of <string> in <replacement>. Option -i tells sed to work within the file on which it’s called, renaming the temporary file sed creates back to the original filename when finished (no temporary file is left over after the deed). For example, let’s replace “[email protected]” in all the text files in the current directory with “[email protected]”:

  # grep -l [email protected] <filenames> | xargs sed -i 's/[email protected]/[email protected]/'

Sometimes, you can play with a command and accomplish a lot, get it just perfect, but, inexplicably, it won't work in the larger script. The single quotes impede the expansion of the shell variables ($HTTP_PORT, etc.). I'm used to single-quoting the match/replace string. If sed doesn't work in your script, try removing the quotes to see if that doesn't fix it.

Observe the two scripts below, one of which works and the other does not. It's the second set that finally worked for me though I had to back-tick the whole thing to get the redirection to work.

These sed statements here worked in isolation (command line trials), but not inserted in the context of a larger script:

	#!/bin/sh
	.
	.
	.
	DEFAULT_HTTP_PORT=8080
	        HTTP_PORT=48080
	 DEFAULT_AJP_PORT=8009
	         AJP_PORT=48009
	.
	.
	.
	rm  -f server.xml.old
	sed 's/$DEFAULT_HTTP_PORT/$HTTP_PORT/g' server.xml > server.xml.1
	sed 's/$DEFAULT_AJP_PORT/$AJP_PORT/g' server.xml.1 > server.xml.2
	mv  server.xml   server.xml.old
	cp  server.xml.2 server.xml
	rm  server.xml.1 server.xml.2
	.
	.
	.

This set worked. All I had to do was remove the single quotes.

	#!/bin/sh
	.
	.
	.
	DEFAULT_HTTP_PORT=8080
	        HTTP_PORT=48080
	 DEFAULT_AJP_PORT=8009
	         AJP_PORT=48009
	.
	.
	.
	rm  -f server.xml.old
	`sed s/$DEFAULT_HTTP_PORT/$HTTP_PORT/g server.xml > server.xml.1`
	`sed s/$DEFAULT_AJP_PORT/$AJP_PORT/g server.xml.1 > server.xml.2`
	mv  server.xml   server.xml.old
	cp  server.xml.2 server.xml
	rm  server.xml.1 server.xml.2
	.
	.
	.