LinuxBBQ

Posted: **Thu Dec 31, 2015 2:59 pm**

We have a Shell Tips & Tricks section which actually covers the builtins of your shell. This section here shows the power of coreutils:

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  [ arch base64 basename cat chcon chgrp chmod chown chroot cksum comm
  coreutils cp csplit cut date dd df dir dircolors dirname du echo env
  expand expr factor false fmt fold groups head hostid hostname id install
  join kill link ln logname ls md5sum mkdir mkfifo mknod mktemp mv nice nl
  nohup nproc numfmt od paste pathchk pinky pr printenv printf ptx pwd
  readlink realpath rm rmdir runcon seq sha1sum sha224sum sha256sum sha384sum
  sha512sum shred shuf sleep sort split stat stdbuf stty sum sync tac tail
  tee test timeout touch tr true truncate tsort tty uname unexpand uniq
  unlink uptime users vdir wc who whoami yes

So let's see if we can collect some tips & tricks here, too.

Posted: **Thu Dec 31, 2015 3:03 pm**

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Merge multiple MP3 to one
Heck, there are programs like mp3wrap or sox, but the best and fastest merging tool for mp3s (or any other audio files) is already there in coreutils. This probably does not work if the bitrates are changing.

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cat song_1.mp3 song_2.mp3 song_3.mp3 song_4.mp3 > side_a.mp3

Bonus tip: if you want to create a slideshow for youtube (so, music and an image), ffmpeg can do that for you:

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ffmpeg -loop 1 -i image.jpg -i side_a.mp3 -c:v libx264 -c:a copy -strict experimental -shortest slideshow.mp4

Create live USB from ISO
This replaces tools like dd. Useful if you want to put an ISO on a device

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cat linuxbbq_anorexicteen.iso /dev/sdb

Live heredoc
This replaces the touch command. If there is no busybox vi or nano available (lol), you can use cat to create files. It takes stdin until you press Ctrl-d

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cat >README.txt

Line Numbering
Nothing special, some people like to have line numbering because they use ed to edit files (lol, NOT!)

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cat -n README.txt

Posted: **Thu Dec 31, 2015 3:40 pm**

Wow. First, I'm surpirsed we have not yet made this thread. Second, I use coreutils everyday, well, at least I thought I was.
What comes first, a need, thus searching and finding a solution which uses a command that we all use often, OR, learning new ways to use a command we use almost daily and looking for use cases to try it out.

Posted: **Thu Dec 31, 2015 5:44 pm**

what drew said. also, some really cool things with cat. did not know it could replace dd. why is there no tool called dog, and if there was what would it do?

here's another cool thing you can do with cat:

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cat bla.txt | grep "anus"

awesome. some more useless stuff here.

sorry i don't have any proper tricks :)

Posted: **Sat Jan 02, 2016 8:19 pm**

there is also my shitey script called CatSSH

http://linuxbbq.org/bbs/viewtopic.php?f=15&t=2188

Posted: **Sun Jan 03, 2016 12:45 pm**

'bout the only one I can think of and use daily:

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mv public_html hacked_public_html_`date -I`

Most people use

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date +%F

which frankly I still can't recall.
(it appends a nice full ISO date, 2016-01-03)
or using cat at work:

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 cat big_data.sql | mysql -u root -p big_data

Posted: **Mon Jan 04, 2016 7:08 pm**

I'm quite fond of the command:

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time cat

What day does Christmas fall on, this year?

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date --date='25 Dec' +%A

Posted: **Mon Jan 04, 2016 9:31 pm**

I think we always use cat to see what our sources list looks like:

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cat /etc/apt/sources.list

When playing with files I often use the rm command:

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rm

wipes the file and:

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rm -r

wipes an entire directory.

But you already know this. ;) coreutils is such a powerful tool in general.

Posted: **Tue Jan 05, 2016 6:26 am**

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df -hl

shows a summary of local disk usage in human readable format

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du -sh ~/.local/share/
du -sh ~/README

shows the disk usage of the directory (or file) in human readable format

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comm FILE1 FILE2

you don't really need 'diff' because 'comm' can do the same, basically

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head -n 10 /etc/inittab

head shows the first n lines of a file, in our case we will know what default runlevel we boot to by default

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tail -f /dev/kmsg

this follows changes at the end of a certain file, in our case the kernel ring buffer (we know this from syslog and dmesg, which is part of util-linux)

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paste FILE1.txt FILE2.txt > FILE_ALL.txt

pastes the content two files, line by line. it is not the same as using cat which pastes file after file. probably useful for databases if you change the delimiter (-d), eg. for CSV

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