Bash Tips

Bash multiprocessing

Supercharge Your Bash Scripts with MultiprocessingFr1nge's Personal Blog

Useful commands

cheat.sh

cheat.sh provides unified access to the best community driven cheat sheets repositories of the world.

# To get a cheat sheet just use the following command
# Change <command> to command name, for instance, ls, id, curl, etc.
$ curl cheat.sh/<command>

# Cheat sheet for curl
$ curl cheat.sh/curl

aria2c

aria2 is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line.

# Multi-thread downloading
$ aria2c -x5 <URL>

# Restarting aria2c continues unfinished download
$ aria2c -x5 <URL>
^C
$ aria2c -x5 <URL> # downloading continues

# Download torrent files (just pass the torrent file to the input)
$ aria2c <name>.torrent

chmod

# Enable all permissions for the owner, write permissions to the group and execute permissions to others
# or rwx-w---x
$ chmod 721 <name>

### Verbose form
# Enable user for rwx
$ chmod u+rwx <name>

# Enable group for w
$ chmod g+w <name>

# Enable others for x
$ chmod o+x <name>

# Enable everyone for x
$ chmod a+x <file>

### Remove permissions (use '-' instead of '+')
# Disable group and others for x
$ chmod og-x <name>

### setuid (4), setgid (2), sticky (1) bits
# Set setgid bit
# or rwxr-sr-x
$ chmod 2755 <name>

## Verbose form
# Set setuid bit 
$ chmod u+s <name>

# Set setgid bit
$ chmod g+s <name>

# Set sticky bit
$ chmod o+t <name>

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

# Case sensitive search
$ find / -name '*some*'

# Case insensitive search
$ find / -iname '*some*'

# ls style output formatting
$ find / -iname '*some*' -ls

# Delete found files (danger: there is no confirmation)
$ find dir_to_delete/ -delete

# Executing a script with search results
# Format: 
#   -exec <command> {} \;
#   <commad> - script/command to execute
#   {} - place for the found file
#   \; - end of <command>
$ find / -iname '*some*' -exec ./script.sh {} \;

grep

# Search string without using regex
# fgrep is an alias for grep -F
$ fgrep

# Using perl-compatible regex (or "real" regex)
$ grep -P

# Searching inside gz archives
$ zgrep

# Highlight found words in search results
$ grep --color=force

# Invert the sense of matching
$ grep -v

# grep by file contents
$ grep -rnw '/path/to/somewhere/' -e 'pattern'

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:

  from IPython import embed; embed()

ncdu

ncdu is a disk usage analyzer with an ncurses interface.

$ ncdu /

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.

$ ./app1 | pv | ./app2
$ cat /dev/urandom | pv | xxd > /dev/null

# cat-like behavior with a progress bar
$ pv file | ./app
$ pv some_file.txt | bzip2 > /dev/null

# tar compression progress bar
$ tar cz /folder | pv > folder.tar.gz

# Network data transfer progress bar
$ pv folder.tar.gz | nc -nlvp 1337

# Monitor other process
$ pv -d PID

# Limit speed
$ pv file.txt -L 2 # 2 bytes per second
$ pv file.txt -L -l 2 # 2 lines per second

ssh

A Visual Guide to SSH Tunnels (with labs)

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

# Create tar archive
$ tar cf archive.tar foo bar

# Create bzip2 archive
$ tar cf archive.tar.bz2 foo bar

# Create gzip archive
$ tar cf archive.tar.gz foo bar

# Extract archive
$ tar xf archive.tar.gz

youtube-dl

youtube-dl is a command-line program to download videos from youtube and other video sites.

$ youtube-dl https://youtu.be/somth12asd34

Modern Unix

GitHub - ibraheemdev/modern-unix: A collection of modern/faster/saner alternatives to common unix commands.GitHub