UNIX - lc00/wiki-experiment GitHub Wiki

File Commands

  • mkdir - Make a directory (-p for nested/file/structure)
  • touch - Create a file
  • cp - Copy (-r for recursive, -i to prompt for overwrites)
  • cmp - Compare files
  • diff - See difference between files. (-i for case-insentive, -B for ignore blanks, -w for ignore whitespace)
    • < - File 1
    • > - File 2
    • d - Delete
    • a - Add
    • c - Change
  • sdiff - Advanced diff. (-s to ignore matches)
    • nothing - Identical
    • < - File 1
    • > - File 2
    • | - Different
  • dircmp - Compare directories
  • ls - List (-a to include hidden files, -l for long form, -R for recursive)
  • mv - Move or rename (-i for interactive)
  • rmdir - Remove directorys (can take multiple)
  • find <directory> "<search string>"
    • -print (display results)
    • -exec compress {} \; (compress the file when you find it)
    • -ok rm {} \; (delete the file when you find it)
  • mtime -4 - (limit results to files modified in the last 4 days)
  • locate <filename> - find system files
  • ln <first file> <second file> - Hard link two files together. (-s for soft link, plus dirs)
    • Hard links are identical, soft links are dependent
  • file <file_name> - Display file metadata
  • split -b 500M big_file.jpg - Splits into 500MB chunks
    • Use cat to recombine
  • sort file_1 file_2 > destination_file - Sort by first character of each line
    • -t, +1 (comma delimited, sort on second field)
    • -u to eliminate duplicates
  • uniq <file_name> - Removes duplicate lines
  • tr a-zA-Z A-Za-z < <file_name> - Translate file
  • fmt <file_name> -w 60 - Format file to a 60 character line
  • wc = word count - -w for words, -l for lines, -c for bytes). Can pipe from ls.

Shell Commands

  • less - Paging (scroll up and down with arrow keys)
  • more - Paging (spacebar, b [if no pipes], q to quit)
  • | - Pipe output to input
  • > - Redirect output to something other than screen
  • >> - Append to output
  • tee - Sends output to multiple locations
    • | tee <first_output> | <second_output>
  • chsh - Change shell
  • tab - Autocomplete, twice for options
    • up, down to search
  • ctrl + a - Beginning of a line, ctrl + e = end of a line
  • stty, stty sane, reset - Fix weird remote issues
  • exit - Quit shell
  • alias - Show a list of aliases
  • alias <new>=<old> - Set a shortcut for the session only
  • ; - Separate commands on the same line
  • && - Same as ;, but only runs if the first one succeeds
  • history <number> - Show lines of history
  • env - Print your environment variables
  • <variable_name>=<value> - Sets a shell variable
  • export <variable_name> - Makes a shell variable an environment variable
  • export <variable_name>=<value> - Set an environment variable
  • echo $<variable_name> - Show a variable

Prompts

  • $PS1 - Regular prompt
  • $PS2 - Secondary prompt
  • %n - Current user
  • %~ - Current directory with path
  • %c - Current directory without path
  • %t - Time
  • %w - Date, no year
  • %W - Date with year
  • \n - Force new line
  • %m - Hostname
  • %M - Hostname with domain

Search Commands

  • cat - Display, can take multiple files, can redirect into another file
  • tac - Reverse cat
  • head/tail -20 - File start or end of file. Can do multiple files.
  • tail -f - "follow" updates
  • grep <needle regex> <haystack> - search. (-5 for context lines, -c for count, -v for all lines that don't match, -i for case-insensitive)
  • ctrl+r - Reverse search through history

awk/sed

  • sed 's/old/new/gim' <source_file> > <destination_file> - Search & replace
    • Can save seds as scripts
    • g = global, i = case-insensitive, m = multiline
  • awk -F, /search/{ <command> $1 } <file_name> - Work with delimited files
    • -F sets delimiter, $1 is the first field
    • Can save awks as scripts

Shells

  • What shells do you have available? cat /etc/shells
  • sh has no completion or aliasing
  • csh allows you to script in C
  • bash/ksh/zsh allows a blend of features and simple scripting
  • Temporarily jump into a shell by executing it
  • zsh autocompletion while cycle through options while tabbing

Tips

  • Multiple commands can be separated with ;
    • && is the same as ;, but only runs if the first one succeeds
  • Find out what shell you’re using with echo $SHELL
  • * is a general wildcard, ? is a single-character wildcard
  • History is in ~/.bash_history - good for stubbing out scripts
  • ^cd^ls runs last command, swapping out cd for ls
  • nano : pico :: vim : vi
  • Find out what group you’re in with grep username /etc/passwd
  • Find out general group info with more /etc/group
  • A t at the end of a permissions list is a "sticky bit", and means it can only be modified by its owner
  • You own any files that you cp
  • Shell variables are tied to the shell, environment variables exist for any shell
  • zsh config is in /etc/zprofile, /etc/zshenv, /etc/zsh/zshrc.
  • User overrides are in ~/.zprofile, ~/.zshrc
  • Edit the PATH= in .zshrc to add more default paths
  • alias <new>=<old> - Set a shortcut. Goes in .zshrc file.
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