Unix tool tip@UnixToolTip

Tips on Unix utilities and related topics from @JohnDCook.

JohnDCook.com
Joined August 2011
205 Photos and videos
'The enjoyment of one's tools is an essential ingredient of successful work.' -- Donald E. Knuth
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The unmount command is umount, no 'n'. Prime candidate for an alias.
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Unix tool tip retweeted
sysxplore
@sysxplore
Sep 25
Now I just think of this old guy whenever I use tar. That’s how I remember it.
sysxplore
@sysxplore
Sep 25
How long have you been using Linux? 20 years. So you must be good with tar commands?
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sha1sum - compute and check SHA1 message digest
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xdg-open will open a file from the commandline using the application associated with its file extension.
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sed command to delete the last line of a file: $d
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Take every 10th line from a file: awk '!(NR % 10)' file
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Automate to save mental energy, not just to save time. johndcook.com/blog/2015/12/2…

Automate to save energy, not time

Automation doesn't always save as much time or effort as we expect. The xkcd cartoon above is looking at automation as an investment. Does the work I put in now eventually save more work than I put...

johndcook.com
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sort -c doesn't sort but checks whether a file is sorted, reporting first exception if not sorted.
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If you only need to know the number of lines in a large file, wc -l is much faster than wc.
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Suppress file name when searching over multiple files: grep -h
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How to replace a character with a newline in Emacs: M-x replace-string RET ; RET C-q C-j.
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Avoiding Multiprocessing Errors in Bash Shell johndcook.com/blog/2024/02/1…

Multiprocess Errors | Bash Shell | Linux | Multithreading

Errors are easy to make when programming multiple concurrent processes or threads. Using atomic operations and well-formed locks can help to avoid such errors.

johndcook.com
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Day of the year: date '+%j'
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Don't copy-paste from a website to a terminal thejh.net/misc/website-termi…
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The GNU version of date lets you do things like the following: date -d 'today + 90 days'
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10 patterns in modern Linux tools that trace back to ed(1) johndcook.com/blog/2026/06/0…

Common patterns in Linux tools that go back to ed(1)

The line editor ed(1) is sort of the Latin of Linux, the ancestor language that initiated patterns that live on in many modern tools and languages.

johndcook.com
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GNU Coreutils Cheat Sheet catonmat.net/blog/gnu-coreut… by @pkrumins

GNU Coreutils Cheat Sheet

A long, long time ago when I was mastering Linux I created three cheat sheets about GNU fileutils, GNU shellutils and GNU textutils. I kept keep them in front of me at all times and I quickly...

catonmat.net
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In bash, !?foo will repeat the most recent command that contained the string 'foo'.
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Minimizing context switching between shell and Python johndcook.com/blog/2019/12/3…

Python REPL and shell integration

Ways to minimize the context interruption when moving between the shell and a Python session.

johndcook.com
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ls -X will group files by extension.
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