Very Useful Linux Commands

A list of commands for general use in linux can be found from the following link:

http://www.tecmint.com/how-to-check-disk-space-in-linux/

An example:

[root@tecmint ~]# df -T

Suppose you want to open a file named pp.dat using vi editor in a linux machine. This can be done using the following command line:

$ vi pp.dat

Suppose you don't want to open the file above using vim editor, but you want to know its contents. All you need to do is to type the following:

$ less pp.dat

Now, you dont know how to move forward or backward. So, you may need to take a look at the help file. Now just type h (it would look like :h) which will take you the following help lines in a well built linux machine. To quit, type :q

SUMMARY OF LESS COMMANDS

Commands marked with * may be preceded by a number, N. Notes in parentheses indicate the behavior if N is given.

h H Display this help. q :q Q :Q ZZ Exit. ---------------------------------------------------------------------------

MOVING

e ^E j ^N CR * Forward one line (or N lines). y ^Y k ^K ^P * Backward one line (or N lines). f ^F ^V SPACE * Forward one window (or N lines). b ^B ESC-v * Backward one window (or N lines). z * Forward one window (and set window to N). w * Backward one window (and set window to N). ESC-SPACE * Forward one window, but don't stop at end-of-file. d ^D * Forward one half-window (and set half-window to N). u ^U * Backward one half-window (and set half-window to N). ESC-) RightArrow * Left one half screen width (or N positions). ESC-( LeftArrow * Right one half screen width (or N positions). F Forward forever; like "tail -f". r ^R ^L Repaint screen. R Repaint screen, discarding buffered input. --------------------------------------------------- Default "window" is the screen height. Default "half-window" is half of the screen height. ---------------------------------------------------------------------------

SEARCHING

/pattern * Search forward for (N-th) matching line. ?pattern * Search backward for (N-th) matching line. n * Repeat previous search (for N-th occurrence). N * Repeat previous search in reverse direction. ESC-n * Repeat previous search, spanning files. ESC-N * Repeat previous search, reverse dir. & spanning files. ESC-u Undo (toggle) search highlighting. &pattern * Display only matching lines --------------------------------------------------- Search patterns may be modified by one or more of: ^N or ! Search for NON-matching lines. ^E or * Search multiple files (pass thru END OF FILE). ^F or @ Start search at FIRST file (for /) or last file (for ?). ^K Highlight matches, but don't move (KEEP position). ^R Don't use REGULAR EXPRESSIONS. ---------------------------------------------------------------------------

JUMPING

g < ESC-< * Go to first line in file (or line N). G > ESC-> * Go to last line in file (or line N). p % * Go to beginning of file (or N percent into file). t * Go to the (N-th) next tag. T * Go to the (N-th) previous tag. { ( [ * Find close bracket } ) ]. } ) ] * Find open bracket { ( [. ESC-^F <c1> <c2> * Find close bracket <c2>. ESC-^B <c1> <c2> * Find open bracket <c1> --------------------------------------------------- Each "find close bracket" command goes forward to the close bracket matching the (N-th) open bracket in the top line. Each "find open bracket" command goes backward to the open bracket matching the (N-th) close bracket in the bottom line.

m<letter> Mark the current position with <letter>. '<letter> Go to a previously marked position. '' Go to the previous position. ^X^X Same as '. --------------------------------------------------- A mark is any upper-case or lower-case letter. Certain marks are predefined: ^ means beginning of the file $ means end of the file ---------------------------------------------------------------------------

CHANGING FILES

:e [file] Examine a new file. ^X^V Same as :e. :n * Examine the (N-th) next file from the command line. :p * Examine the (N-th) previous file from the command line. :x * Examine the first (or N-th) file from the command line. :d Delete the current file from the command line list. = ^G :f Print current file name. ---------------------------------------------------------------------------

MISCELLANEOUS COMMANDS

-<flag> Toggle a command line option [see OPTIONS below]. --<name> Toggle a command line option, by name. _<flag> Display the setting of a command line option. __<name> Display the setting of an option, by name. +cmd Execute the less cmd each time a new file is examined.

!command Execute the shell command with $SHELL. |Xcommand Pipe file between current pos & mark X to shell command. v Edit the current file with $VISUAL or $EDITOR. V Print version number of "less". ---------------------------------------------------------------------------

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LINE EDITING

These keys can be used to edit text being entered on the "command line" at the bottom of the screen.

RightArrow ESC-l Move cursor right one character. LeftArrow ESC-h Move cursor left one character. CNTL-RightArrow ESC-RightArrow ESC-w Move cursor right one word. CNTL-LeftArrow ESC-LeftArrow ESC-b Move cursor left one word. HOME ESC-0 Move cursor to start of line. END ESC-$ Move cursor to end of line. BACKSPACE Delete char to left of cursor. DELETE ESC-x Delete char under cursor. CNTL-BACKSPACE ESC-BACKSPACE Delete word to left of cursor. CNTL-DELETE ESC-DELETE ESC-X Delete word under cursor. CNTL-U ESC (MS-DOS only) Delete entire line. UpArrow ESC-k Retrieve previous command line. DownArrow ESC-j Retrieve next command line. TAB Complete filename & cycle. SHIFT-TAB ESC-TAB Complete filename & reverse cycle. CNTL-L Complete filename, list all.

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