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Replace "foo" with "bar" in all files in current directory recursively
This is a slightly modified version of http://www.commandlinefu.com/commands/view/4283/recursive-search-and-replace-old-with-new-string-inside-files (which did not work due to incorrect syntax) with the added option to sed inside only files named filename.ext
Remove the dashes from a UUID using bash search and replace.
using find's exec option instead of a for loop and using sed's -i option for inplace replacement. no need to do the file swap.
Use sed to edit in-place a list of files returned by find.
In this simple example the command will add a comma to the end of every line except the last. I found this really useful when programatically constructing sql scripts. See sample output for example.
I needed a way to search all files in a web directory that contained a certain string, and replace that string with another string. In the example, I am searching for "askapache" and replacing that string with "htaccess". I wanted this to happen as a cron job, and it was important that this happened as fast as possible while at the same time not hogging the CPU since the machine is a server.
So this script uses the nice command to run the sh shell with the command, which makes the whole thing run with priority 19, meaning it won't hog CPU processing. And the -P5 option to the xargs command means it will run 5 separate grep and sed processes simultaneously, so this is much much faster than running a single grep or sed. You may want to do -P0 which is unlimited if you aren't worried about too many processes or if you don't have to deal with process killers in the bg.
Also, the -m1 command to grep means stop grepping this file for matches after the first match, which also saves time.