Commands by ketil

Commands by ketil (3)

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Poor man's unsort (randomize lines)

If you need to randomize the lines in a file, but have an old sort commands that doesn't support the -R option, this could be helpful. It's easy enough to remember so that you can create it as a script and use that. It ain't real fast. It ain't safe. It ain't super random. Do not use it on untrusted data. It requires bash for the $RANDOM variable to work. Show Sample Output
This is sample output - yours may be different.
```
$ echo -e a\\nb\\nc | while read l; do echo $RANDOM "$l"; done | sort -n | cut -d " " -f 2-
c
a
b
```
0

while read l; do echo $RANDOM "$l"; done | sort -n | cut -d " " -f 2-

ketil · 2010-02-03 22:36:34 5
grep (or anything else) many files with multiprocessor power

xargs -P N spawns up to N worker processes. -n 40 means each grep command gets up to 40 file names each on the command line.
This is sample output - yours may be different.
4

find . -type f -print0 | xargs -0 -P 4 -n 40 grep -i foobar

ketil · 2009-08-05 23:18:44 8
Send email with one or more binary attachments

This command uses mutt to send the mail. You must pipe in a body, otherwise mutt will prompt you for some stuff. If you don't have mutt, it should be dead easy to install.
This is sample output - yours may be different.
11

echo "Body goes here" | mutt -s "A subject" -a /path/to/file.tar.gz recipient@example.com

ketil · 2009-08-05 23:06:25 10

What's this?

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Merge files, joining each line in one line

Change every instance of OLD to NEW in file FILE

Very quick way to change a word in a file. I use it all the time to change variable names in my PHP scripts (sed -i 's/$oldvar/$newvar/g' index.php)

Check syntax of all Perl modules or scripts underneath the current directory

Finds all *.p[ml]-files and runs a perl -c on them, checking whether Perl thinks they are syntactically correct

Find usb device in realtime

Using this command you can track a moment when usb device was attached.

Remind yourself to leave in 15 minutes

If you spend most of your time in front of the terminal, leave is a useful reminder. Leave can have absolute form: leave 1555 reminds you to leave at 3:55PM

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)

Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

Creates a symbolic link or overwrites an existing one

-n: dereference the existing link -v: (optional) to be sure of what is being done -f: force the deletion of the existing one -s: creates a symlink Be careful: the destination can also be a file or a directory and it will be overwritten.

Write comments to your history.

A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

Create multiple subfolders in one command.

Instead of typing separate commands to create various subfolders, we can create multiple subfolders by listing them between brackets and separated by commas.

Monitor changed files into a log file, with day rotation, using fswatch (MacOS)

This command monitors changes in the current folder structure (subfolders included) and files, and log it into a hidden file in the same folder, called `.file_changes_YYMMDD.log`. Modify the `--exclude` parameters to define what should be skipped.

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