Some very basic linux commands for quick reference.

• ls: list files
  • ls, basic list
  • ls -l, one per line, long format
  • ls -a, list all files, including hidden file
  • ls -la, combination of the two
  • ls -lh, with file size in human readable format
  • ls -lS, long format list sorted by size (descending)
  • ls -lt, sort by modification time, newest first
  • ls -ltr, sort by time in reverse order
• less: open file and read by page
  • less source_file, open a file and onle show the first page, less
  • d to next page; p to previous page
  • g to start; G to end
  • /kw for forward search; ?kw for backword search; n next and N previous
  • q to quit
• cp: copy file or folder
  • cp /path/to/origin /path/to/copy, copy file
  • cp -r /path/to/origin /path/to/copy, copy folder, recursive
  • cp -vr /path/to/origin /path/to/copy, verbose mode, show it
  • file name can be specified with wildcard
• mv: move or rename files and directories
  • mv source target, move or rename
  • mv -v source target, verbose mode
  • mv -f source target, overwriting with out confirmation
• rm: remove files or directories
  • rm /path/to/file, remove file
  • rm -r /path/to/folder, remove folder, recursively
  • rm -rf /path/to/folder, remove folder without prompt
  • rm -i /path/to/file, interactive mode, need confirmation
  • before use rm with wildcards, try it with ls first
• wildcard: match filename
  • *, match any characters
  • ?, match any single character
  • [characters], match member character of set
    • [abc], match a, b or c
    • [:alnum:], match alphanumeric characters
    • [:alpha:], match alphabetic characters
    • [:digit:], match numerals
    • [:upper:], match uppercase alphabetic characters
    • [:lower:], match lowercase alphabetic characters
  • [!characters], match opposite of [characters]
• I/O Redirection
  • stdout: redirect standard output to file
    • ls, by default to standard output, like display
    • ls > file_list.txt, use > to redirect, write mode
    • ls >> file_list.txt, use » to redirect, append mode
  • stdin: get standard input from file
    • sort < file_list.txt, use < as standard input
    • sort < file_list.txt > sort_file_list.txt, combine stdin and stdout
  • pipelines |: stdout of one cmd is fed into the stdin of another
    • ls -l | less, powerful pipeline |
    • ls -lt | head -5, dispalys 5 newest files
    • du | sort -nr, display list of dirs and space consumed, sort it, largest first
  • filter: take stdin, perfrom operation, send results to stdout
    • sort:
      • sort filename, sort a file in ascending order
      • sort -r filename, sort a file in descending order
      • sort -n filename, sort a file using numeric rather than alphabetic order
      • sort -u filename, sort and preserve only unique lines
    • uniq: return unique line, needs to be sorted first
      • sort file | uniq, display each line once
      • sort file | uniq -u, display only unique lines
      • sort file | uniq -d, display only duplicated lines
      • sort file | uniq -c, display unique lines with occurences
      • sort file | uniq -c | sort -nr
    • grep: examine lines of input, output lines that contain the pattern
      • grep query_string path/to/file, search for an eaxct string
      • grep -i query_string path/to/file, in case-insensitive mode
      • grep -rI query_string ., search current dir recursively, ignore binary file
      • grep -C 3 query_string path/to/file, context with 3 lines
      • grep -c query_string path/to/file, count of match instead of matching text
      • grep -n query_string path/to/file, line number for each match
      • grep -l query_string path/to/file, list of files with matches
      • cat path/to/file | grep query_string, search stdin using pipeline
    • head: output the first part of files
      • head -n count_of_lines filename, first n lines
      • head -c number_in_bytes filename, first n bytes
    • tail: output the last part of files
      • tail -n count_of_lines filename, last n lines
      • tail -c number_in_bytes filename, last n bytes
• unzip: extract compressed files in a zip archive
  • unzip file, extract zip file
  • unzip compressed_file -d /path/to/put/extracted_file, extract zip file to folder
  • unzip -l file, list the contents of a zip file without extracting
  • zip, unzip, gzip, gunzip, tar…
• ssh: ssh user@your_ip
• nohup: Allows for a process to live when the terminal gets killed
  • nohup command options
  • nohup command options &, run in the background
• linux command