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Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.
Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):
Subscribe to the feed for:
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.
find . -type f -newermt "3 years ago" ! -newermt "2 years ago"
find . -type f -newermt "last monday"
Move efficiently between directories.
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.
Note: I don't want to alter $HOME because then all my dot files will move.
Change directory to "dir" (using CDPATH if necessary)
Change directory to "dir" (containing folder of "file.txt")
This allows you to cut'n'paste, or use
CDDIR is unset
Change directory to $HOME
Change directory to /home/flatcap/work
For convenience, put the command, and the following, in your .bashrc or .bash_profile
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.
"\*.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 :-)
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.