Just wanted to share an alias I have in use and found it useful again. It’s a simple wrapper around xargs, which I always forget how to use properly, so I set up an alias for. All it does is operate on each line on stdout.
The arguments are interpreted as the command to execute. The only thing to remember is using the {} as a placeholder for the input line. Look in the examples to understand how its used.
# Pipe each line and execute a command. The "{}" will be replaced by the line.
#
# Example:
# cat url.txt | foreach echo download {} to directory
# ls -1 | foreach echo {}
# find . -maxdepth 2 -type f -name 'M*' | foreach grep "USB" {}
alias foreach='xargs -d "\n" -I{}'
Useful for quickly operating on each line of a file (in example to download from list of urls) or do something with any stdout output line by line. Without remembering or typing a for loop in terminal.
Nice! I used to do something like this, which avoids xargs altogether:
cat urls.txt | while read url; do echo download $url; doneYou can also avoid cat since you aren’t actually concatenating files (depending on file size this can be much faster):
Usually this is the way. Once you enter xargs’ world, you lose access to your shell aliases, functions, and un-exported variables, which will often bite you in the ass.
You should use
-roption forreadcommand to preserve backslashes. I was usingwhileloops before too, but wanted to have a compact single command replacement. And doing it with awhileloop as an alias (or function) didn’t work well, because the command has to be interpreted.xargsdoes exactly that, as it is designed for this kind of stuff. Other than having less stuff to type, I wonder if there are benefits from one over the otherwhilevsxargs. In a script, I prefer writing fullwhileloops instead.