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Finding Files

3.3.2 Multiple Files

Sometimes you need to process files alone. But when you don't, it is faster to run a command on as many files as possible at a time, rather than once per file. Doing this saves on the time it takes to start up the command each time.

To run a command on more than one file at once, use the xargs command, which is invoked like this:

xargs [option...] [command [initial-arguments]]

xargs reads arguments from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines. It executes the command (default is `/bin/echo') one or more times with any initial-arguments followed by arguments read from standard input. Blank lines on the standard input are ignored.

Instead of blank-delimited names, it is safer to use `find -print0' or `find -fprint0' and process the output by giving the `-0' or `--null' option to GNU xargs, GNU tar, GNU cpio, or perl.

You can use shell command substitution (backquotes) to process a list of arguments, like this:

grep -l sprintf `find $HOME -name '*.c' -print`

However, that method produces an error if the length of the `.c' file names exceeds the operating system's command-line length limit. xargs avoids that problem by running the command as many times as necessary without exceeding the limit:

find $HOME -name '*.c' -print | grep -l sprintf

However, if the command needs to have its standard input be a terminal (less, for example), you have to use the shell command substitution method.

3.3.2.1 Unsafe File Name Handling
3.3.2.2 Safe File Name Handling
3.3.2.3 Limiting Command Size
3.3.2.4 Interspersing File Names