Commands by flatcap

Quietly get a webpage from wikipedia: curl -s

By default, don't output anything: sed -n

Search for interesting lines: /<tr valign="top">/

With the matching lines: {}

Search and replace any html tags: s/<[^>]*>//g

Finally print the result: p

Show the crontabs of all the users.

If your locale has Monday as the first day of the week, like mine in the UK, change the two $7 into $6

Find files matching multiple descriptions (*.c and *.cpp) excluding multiple directories (unit-test and android).

Search for files and list the 20 largest.

gives us a list of file, recursively, starting from here (.)

separate the names of files with NULL characters, so we're not confused by spaces

then xargs run the du command to find their size (in human-readable form -- 64M not 64123456)

use sort to arrange the list in size order. sort -h knows that 1M is bigger than 9K

finally only select the top twenty out of the list

Take a file and ,."()?!;: give a list of all the words in order of increasing length.

First of all use tr to map all alphabetic characters to lower case and also strip out any puntuation.

A-Z become a-z

,."()?!;: all become \n (newline)

I've ignored - (hyphen) and ' (apostrophe) because they occur in words.

Next use bash to print the length ${#w} and the word

Finally sort the list numerically (sort -n) and remove any duplicates (sort -u).

Note: sort -nu performs strangely on this list. It outputs one word per length.

Count the number of active connections to a MySQL database.

The MySQL command "show processlist" gives a list of all the active clients.

However, by using the processlist table, in the information_schema database, we can sort and count the results within MySQL.

List the full path of some files.

You can add ".*" on the end if you want to display hidden files.

Print all lines between two line numbers

This command uses sed(1) to print all lines between two known line numbers in a file. Useful for seeing output in a log file, where the line numbers are known. The above command will print all lines between, and including, lines 3 and 6.

Remove the dashes from a UUID using bash search and replace.

Find the package a file belongs to on an rpm-based distro.

Find information about the rpm package which owns a certain file.

Find files in a specific date range - in this case, the first half of last year.

-newermt = modification time of the file is more recent than this date

GNU find allows any date specfication that GNU date would accept, e.g.

or

Move efficiently between directories.

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This command adds a couple of extra features to cd, without affecting normal use.

CDPATH use is also unaffected. It introduces and environment variable CDDIR which is used as an alternate home directory.

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Note: I don't want to alter $HOME because then all my dot files will move.

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Examples:

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Change directory to "dir" (using CDPATH if necessary)

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Change directory to "dir" (containing folder of "file.txt")

This allows you to cut'n'paste, or use

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CDDIR is unset

Change directory to $HOME

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CDDIR=/home/flatcap/work

Change directory to /home/flatcap/work

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For convenience, put the command, and the following, in your .bashrc or .bash_profile

export CDDIR="/home/flatcap/work"

alias cdd="CDDIR=$(pwd)"

Give files a random name (don't ask why :-)

The function will rename files but maintain their extensions.

BUG: If a file doesn't have an extension it will end up with a dot at the end of the name.

The parameter '8' for pwgen controls the length of filenames - eight random characters.

Recursively find php files and replace tab characters with spaces.

Options:

"\*.php" -- replace this with the files you wish to find

"expand" -- replace tabs with spaces (use "unexpand" to replace spaces with tabs)

"-t4" -- tabs represent 4 spaces

Note: The IFS="" in the middle is to prevent 'read' from eating leading/trailing whitespace in filenames.

Select a file/folder at random.

Countdown clock - Counts down from $MIN minutes to zero.

I let the date command do the maths.

This version doesn't use seq.

Are the two strings anagrams of one another?

sed splits up the strings into one character per line

the result is sorted

cmp compares the results

Note: This is not pretty. I just wanted to see if I could do it in bash.

Note: It uses fewer characters than the perl version :-)

Take a folder full of files and split it into smaller folders containing a maximum number of files. In this case, 100 files per directory.

find creates the list of files

xargs breaks up the list into groups of 100

for each group, create a directory and copy in the files

Note: This command won't work if there is whitespace in the filenames (but then again, neither do the alternative commands :-)

http://en.wikipedia.org/wiki/Pascal%27s_triangle

This one's for bartonski. Enjoy.

132 characters. I'm sure we can do better.

Note: after row 64 we overflow integer maths.

Calculate pi from the infinite series 4/1 - 4/3 + 4/5 - 4/7 + ...

This expansion was formulated by Gottfried Leibniz: http://en.wikipedia.org/wiki/Leibniz_formula_for_pi

I helped rubenmoran create the sum of a sequence of numbers and he replied with a command for the sequence: 1 + 2 -3 + 4 ...

This set me thinking. Transcendental numbers!

seq provides the odd numbers 1, 3, 5

sed turns them into 4/1 4/3 4/5

paste inserts - and +

bc -l does the calculation

Note: 100 million iterations takes quite a while. 1 billion and I run out of memory.