Useful Linux commands and their arguments
🔸 cd /directory moves the present working directory to one specified
🔸 cp /copied_item /target copies a filed or directory to a target directory. If your copying a directory use cp -rf . .
🔸 pwd shows the absolute path of where you are (present working directory)
🔸 chmod ### file how you give or remove access to files. first digit is you, second is group and last is all users
(read=4,write=2,execute=1. ex: use 777 for full access to everyone)
🔸 diff /file /file outputs the lines that do not match between the two files
🔸 rm file remove command lets you remove a file. Removing a directory requires -rf (ex: rm -rf dir)
🔸 mkdir directoryname makes a directory with the name specified
🔸 touch filename makes a file with the name specified
🔸 mv file file lets you move a file somewhere else and is also used to rename files
🔸 cat file displays the text of a file
🔸 man "command" displays the manual for the command specified. Useful to find options for the command quickly
🔸 history shows the commands you've entered
🔸 ctrl+c quits you out of most programs
🔸 | this symbol is called "pipe" and is used to feed output of one command into another command without
storing it into a variable (ex: "ls -s | head -5" takes the list of files ordered by size from ls and prints the top 5 of them)
ls commands $ ls [options] [file|dir]
🔸 ls -a list all files including hidden file starting with '.'
🔸 ls --color colored list [=always/never/auto]
🔸 ls -d list directories
🔸 ls -i list file's inode index number
🔸 ls -l list with long format - show permissions
🔸 ls -la list long format including hidden files
🔸 ls -lh list long format with readable file size
🔸 ls -ls list with long format with file size
🔸 ls -r list in reverse order
🔸 ls -R list recursively directory tree
🔸 ls -s list file size
🔸 ls -S sort by file size
🔸 ls -t sort by time & date
🔸 ls -X sort by extension name
grep commands grep [options] pattern [files]
🔸 grep -c This prints only a count of the lines that match a pattern
🔸 grep -h Display the matched lines, but do not display the filenames
🔸 grep -i Ignores, case for matching
🔸 grep -l Displays list of a filenames only
🔸 grep -n Display the matched lines and their line numbers
🔸 grep -v This prints out all the lines that do not matches the pattern
🔸 grep -e exp Specifies expression with this option. Can use multiple times
🔸 grep -f file Takes patterns from file, one per line
🔸 grep -E Treats pattern as an extended regular expression (ERE)
🔸 grep -w Match whole word
sed commands sed [option] 'command' [input-file]
🔸 sed '/^$/d' Remove all whitespace
🔸 sed 's/Sonday/Sunday/' weekday.txt
🔸 sed -i When option, edit source file directly. Also used to ignore case when flag
🔸 sed -g Edit every occurence
🔸 ^ Acts like a special character and matches at the beginning of the regular exp
🔸 $ Acts like a special character and matches at the end of the regular exp
🔸 . Matches any single character, even including a new line
🔸 * Matches the sequence of zero or more instances of the previous character
🔸 sed 's/Linux/Unix/' linuxteck.txt (first occurence in each line)
🔸 sed 's/Linux/Unix/2' linuxteck.txt (Second occurence in each line)
sort commands sort [OPTION]... [FILE]...
🔸 sort -b Remove all whitespace
🔸 sort -d Consider only blanks and alphanumeric characters
🔸 sort -f Fold lower case to upper case characters
🔸 sort -g Compare according to general numerical value
🔸 sort -i Consider only printable characters
🔸 sort -n Compare according to string numerical value
head commands head [OPTION]... [FILE]...
🔸 head -n # Print number of lines from top down
🔸 tail -# prints last # of elements (lines/files)