# Bash Tips ![](https://drawings.jvns.ca/drawings/bashtips.png) ## Bash multiprocessing {% embed url="" %} ## Useful commands ### cheat.sh [cheat.sh](https://github.com/chubin/cheat.sh) provides unified access to the best community driven cheat sheets repositories of the world. ```bash # To get a cheat sheet just use the following command # Change to command name, for instance, ls, id, curl, etc. $ curl cheat.sh/ # Cheat sheet for curl $ curl cheat.sh/curl ``` ### aria2c [aria2](https://github.com/aria2/aria2) is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line. ```bash # Multi-thread downloading $ aria2c -x5 # Restarting aria2c continues unfinished download $ aria2c -x5 ^C $ aria2c -x5 # downloading continues # Download torrent files (just pass the torrent file to the input) $ aria2c .torrent ``` ### chmod ```bash # Enable all permissions for the owner, write permissions to the group and execute permissions to others # or rwx-w---x $ chmod 721 ### Verbose form # Enable user for rwx $ chmod u+rwx # Enable group for w $ chmod g+w # Enable others for x $ chmod o+x # Enable everyone for x $ chmod a+x ### Remove permissions (use '-' instead of '+') # Disable group and others for x $ chmod og-x ### setuid (4), setgid (2), sticky (1) bits # Set setgid bit # or rwxr-sr-x $ chmod 2755 ## Verbose form # Set setuid bit $ chmod u+s # Set setgid bit $ chmod g+s # Set sticky bit $ chmod o+t ``` ### curl [curl](https://github.com/curl/curl) a command line tool and library for transferring data with URL syntax. Useful operation mode: * [-o, --output ](https://curl.se/docs/manpage.html#-o)- write output to `file` instead of stdout. * [-X, --request ](https://curl.se/docs/manpage.html#-X)- specifies a custom request method to use when communicating with the HTTP server. * [-H, --header ](https://curl.se/docs/manpage.html#-H)
- extra header to include in the request when sending HTTP to a server. * [-d, --data ](https://curl.se/docs/manpage.html#-d)- adds body to the request. * [--path-as-is](https://curl.se/docs/manpage.html#--path-as-is) - tell curl to not handle sequences of `/../` or `/./` in the given URL path. * [-v, --verbose](https://curl.se/docs/manpage.html#-v) - makes curl verbose during the operation. ### find ```bash # 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 {} \; # - script/command to execute # {} - place for the found file # \; - end of $ find / -iname '*some*' -exec ./script.sh {} \; ``` ### grep ```bash # 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](https://github.com/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: ```python from IPython import embed; embed() ``` ### ncdu [ncdu](https://dev.yorhel.nl/ncdu) is a disk usage analyzer with an ncurses interface. ```bash $ ncdu / ``` Useful hotkeys: * Navigation by arrows * `s` - sort by size * `C` - sort by quantity * `c` - show quantity * `d` - delete ### pv [pv](https://linux.die.net/man/1/pv) - monitor the progress of data through a pipe. ```bash $ ./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 {% embed url="" %} ### tar [tar](https://linux.die.net/man/1/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 ```bash # 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](https://github.com/ytdl-org/youtube-dl) is a command-line program to download videos from youtube and other video sites. ```bash $ youtube-dl https://youtu.be/somth12asd34 ``` ### Modern Unix {% embed url="" %} --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://0xn3va.gitbook.io/cheat-sheets/linux/bash-tips.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.