If you need to perform a command a second time on a different file, you can use command replacement with the ^ symbol. e.g. cp foo.txt /to/some/directory then ^foo^bar, expanding to: cp bar.txt /to/some/directory.
To find information about a particular command, the apropos utility can be very helpful, this will search the system and find any matching manual pages for a certain command.
Here is an example.
┌─[✗]─[jason@darkstar]─[~] └──╼ $apropos fdisk cfdisk (8) - display or manipulate a disk partition table fdisk (8) - manipulate disk partition table sfdisk (8) - display or manipulate a disk partition table |
Use the help command to get information about a bash scripting command. This can really help out if you are stuck on a scripting issue and need help.
┌─[jason@darkstar]─[~] └──╼ $help echo echo: echo [-neE] [arg ...] Write arguments to the standard output. Display the ARGs, separated by a single space character and followed by a newline, on the standard output. Options: -n do not append a newline -e enable interpretation of the following backslash escapes -E explicitly suppress interpretation of backslash escapes `echo' interprets the following backslash-escaped characters: \a alert (bell) \b backspace \c suppress further output \e escape character \E escape character \f form feed \n new line \r carriage return \t horizontal tab \v vertical tab \[tab]backslash \0nnn the character whose ASCII code is NNN (octal). NNN can be 0 to 3 octal digits \xHH the eight-bit character whose value is HH (hexadecimal). HH can be one or two hex digits Exit Status: Returns success unless a write error occurs. |
Use it like this to get more verbose help output.
┌─[jason@darkstar]─[~] └──╼ $help -m echo |
Print only a short usage synopsis for each command.
┌─[jason@darkstar]─[~] └──╼ $help -s echo echo: echo [-neE] [arg ...] |
Another way to get information about a certain Linux command. The whatis command returns a short description of a Linux command you are curious about.
┌─[✗]─[jason@darkstar]─[~] └──╼ $whatis ls ls (1) - list directory contents |
The free command tells you the status of your memory and swap, how much you have used and how much you have left.
To make a backup without typing the full path twice: cp /long/path/to/file/name{,.orig} to create a copy with the suffix .orig.
Use lsof to find out which process has open handles for a file. ‘lsof +D /path’ will find all processes for the given path. This is useful for unmounting media.
Edit the command line with cut and paste: ctrl-k for cut, and ctrl-y for paste.
To manage Apache modules use “a2enmod” to enable and “a2dismod” to disable.
e.g. sudo a2enmod rewrite