Commands tagged xargs

This can be useful for transforming command-line args into input for xargs (one per line). This can also be done with ls if the args are filenames, but that's getting awfully close to Useless Use of Cat territory (http://partmaps.org/era/unix/award.html).

Similar to xargs -i, but works with builtin bash commands (rather than running "bash -c ..." through xargs)

Preserve file structure when coping and exclude some file o dir patterns

Convert all jpegs in the current directory into ~1024*768 pixels and ~ 150 KBytes jpegs

recursive find and replace. important stuff are grep -Z and zargs -0 which add zero byte after file name so sed can work even with file names with spaces.

Do the same as pssh, just in shell syntax.

Put your hosts in hostlist, one per line.

Command outputs are gathered in output and error directories.

for when a program is hogging the sound output. finds, and kills. add -9 to the end for wedged processes. add in 'grep ^program' after lsof to filter.

Gnu grep allows to restrict the search to files only matching a given pattern. It also allows to exclude files.

I like this better than some of the alternatives using -exec, because if I want to change the string, it's right there at the end of the command line. That means less editing effort and more time to drink coffee.

The thunderbird message datastores get corrupt some times causing random failures, compaction to fail and general suck in thunderbird. Removing them causes thunderbird to rebuild the indexes and makes things quick again.

Works with files containing spaces and for very large directories.

Find and kill multiple instances of a process with one simple command.

Warning!, if the pattern didn't find anything it shows the total size of dot dir

Finds all C++, Python, SWIG files in your present directory (uses "*" rather than "." to exclude invisibles) and counts how many lines are in them. Returns only the last line (the total).

There is a limit to how many processes you can run at the same time for each user, especially with web hosts. If the maximum # of processes for your user is 200, then the following sets OPTIMUM_P to 100.

This is very useful in scripts because this is such a fast low-resource-intensive (compared to ps, who, lsof, etc) way to determine how many processes are currently running for whichever user. The number of currently running processes is subtracted from the high limit setup for the account (see limits.conf, pam, initscript).

An easy to understand example- this searches the current directory for shell scripts, and runs up to 100 'file' commands at the same time, greatly speeding up the command.

I am using it in my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html especially for the xargs command. Xargs has a -P option that lets you specify how many processes to run at the same time. For instance if you have 1000 urls in a text file and wanted to download all of them fast with curl, you could download 100 at a time (check ps output on a separate [pt]ty for proof) like this:

I like to do things as fast as possible on my servers. I have several types of servers and hosting environments, some with very restrictive jail shells with 20processes limit, some with 200, some with 8000, so for the jailed shells my xargs -P10 would kill my shell or dump core. Using the above I can set the -P value dynamically, so xargs always works, like this.

If you were building a process-killer (very common for cheap hosting) this would also be handy.

Note that if you are only allowed 20 or so processes, you should just use -P1 with xargs.

You WILL have problems if the files have the same name.

Use cases: consolidate music library and unify photos (especially if your camera separates images by dates).

After running the command and verifying if there was no name issues, you can use

to remove now empty subdirectories.

Parallel does not suffer from the risk of mixing of output that xargs suffers from. -j+0 will run as many jobs in parallel as you have cores.

With parallel you only need -0 (and -print0) if your filenames contain a '\n'.

Parallel is from https://savannah.nongnu.org/projects/parallel/

If a directory name contains space xargs will do the wrong thing. Parallel https://savannah.nongnu.org/projects/parallel/ deals better with that.

This deals nicely with files having special characters in the file name (space ' or ").

Parallel is from https://savannah.nongnu.org/projects/parallel/