Bash Tips

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Bash Tips
Bash multiprocessing
Supercharge Your Bash Scripts with Multiprocessing
Fr1nge's Personal Blog
Useful commands
cheat.sh
​cheat.sh provides unified access to the best community driven cheat sheets repositories of the world.
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# To get a cheat sheet just use the following command
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# Change <command> to command name, for instance, ls, id, curl, etc.
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$ curl cheat.sh/<command>
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​
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# Cheat sheet for curl
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$ curl cheat.sh/curl
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aria2c
​aria2 is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line.
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# Multi-thread downloading
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$ aria2c -x5 <URL>
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​
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# Restarting aria2c continues unfinished download
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$ aria2c -x5 <URL>
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^C
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$ aria2c -x5 <URL> # downloading continues
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​
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# Download torrent files (just pass the torrent file to the input)
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$ aria2c <name>.torrent
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chmod
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# Enable all permissions for the owner, write permissions to the group and execute permissions to others
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# or rwx-w---x
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$ chmod 721 <name>
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​
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### Verbose form
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# Enable user for rwx
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$ chmod u+rwx <name>
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​
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# Enable group for w
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$ chmod g+w <name>
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​
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# Enable others for x
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$ chmod o+x <name>
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​
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# Enable everyone for x
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$ chmod a+x <file>
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​
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### Remove permissions (use '-' instead of '+')
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# Disable group and others for x
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$ chmod og-x <name>
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​
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### setuid (4), setgid (2), sticky (1) bits
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# Set setgid bit
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# or rwxr-sr-x
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$ chmod 2755 <name>
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​
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## Verbose form
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# Set setuid bit 
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$ chmod u+s <name>
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​
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# Set setgid bit
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$ chmod g+s <name>
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​
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# Set sticky bit
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$ chmod o+t <name>
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curl
​curl a command line tool and library for transferring data with URL syntax.
Useful operation mode:
​-o, --output - write output to file instead of stdout.
​-X, --request - specifies a custom request method to use when communicating with the HTTP server.
​-H, --header ​header/@file - extra header to include in the request when sending HTTP to a server.
​-d, --data - adds body to the request.
​--path-as-is - tell curl to not handle sequences of /../ or /./ in the given URL path.
​-v, --verbose - makes curl verbose during the operation.
find
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# Case sensitive search
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$ find / -name '*some*'
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​
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# Case insensitive search
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$ find / -iname '*some*'
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​
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# ls style output formatting
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$ find / -iname '*some*' -ls
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​
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# Delete found files (danger: there is no confirmation)
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$ find dir_to_delete/ -delete
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​
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# Executing a script with search results
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# Format: 
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#   -exec <command> {} \;
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#   <commad> - script/command to execute
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#   {} - place for the found file
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#   \; - end of <command>
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$ find / -iname '*some*' -exec ./script.sh {} \;
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grep
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# Search string without using regex
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# fgrep is an alias for grep -F
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$ fgrep
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​
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# Using perl-compatible regex (or "real" regex)
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$ grep -P
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​
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# Searching inside gz archives
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$ zgrep
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​
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# Highlight found words in search results
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$ grep --color=force
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​
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# Invert the sense of matching
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$ grep -v
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​
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# grep by file contents
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$ grep -rnw '/path/to/somewhere/' -e 'pattern'
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ipython
​ipython is a handy command shell for python, which supports:
Tab completion
Help by .method? + enter
Embedding in a script for debugging using the interactive shell:
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from IPython import embed; embed()
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ncdu
​ncdu is a disk usage analyzer with an ncurses interface.
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$ ncdu /
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Useful hotkeys:
Navigation by arrows
s - sort by size
C - sort by quantity
c - show quantity
d - delete
pv
​pv - monitor the progress of data through a pipe.
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$ ./app1 | pv | ./app2
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$ cat /dev/urandom | pv | xxd > /dev/null
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​
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# cat-like behavior with a progress bar
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$ pv file | ./app
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$ pv some_file.txt | bzip2 > /dev/null
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​
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# tar compression progress bar
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$ tar cz /folder | pv > folder.tar.gz
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​
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# Network data transfer progress bar
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$ pv folder.tar.gz | nc -nlvp 1337
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​
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# Monitor other process
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$ pv -d PID
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​
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# Limit speed
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$ pv file.txt -L 2 # 2 bytes per second
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$ pv file.txt -L -l 2 # 2 lines per second
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tar
​tar saves many files together into a single tape or disk archive, and can restore individual files from the archive.
Useful operation mode:
-c - create a new archive
-f - use archive file or device ARCHIVE
-j, --bzip2 - compress/decompress the archive through bzip2
-z, --gzip - compress/decompress the archive through gzip
-t, --list - list the contents of an archive
-x - extract files from an archive
-C, --directory=DIR - change output directory to DIR
-v verbosely list files processed
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# Create tar archive
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$ tar cf archive.tar foo bar
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​
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# Create bzip2 archive
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$ tar cf archive.tar.bz2 foo bar
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​
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# Create gzip archive
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$ tar cf archive.tar.gz foo bar
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​
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# Extract archive
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$ tar xf archive.tar.gz
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youtube-dl
​youtube-dl is a command-line program to download videos from youtube and other video sites.
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$ youtube-dl https://youtu.be/somth12asd34
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Modern Unix
GitHub - ibraheemdev/modern-unix: A collection of modern/faster/saner alternatives to common unix commands.
GitHub
User Space vs Kernel Space
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