WriteBash - To get help for shell builtins, use the help command. Why is that?
In Linux, we have a lot of commands. And the commands have different instructions and usage options. We can’t remember all the commands with all the options, I’m pretty sure about that. So we need help.
Use the help command to get help for shell builtins
The name of the command can tell you what it means. However, the
help command is only used with builtins shells.
help command can only display help for shell builtins.
What is its syntax? Pretty simple as every other command, you look below.
$ help command
I will do some examples with the
help command. First I will try it with the
ls command. Through the previous article, you know that the
ls command is not a builtin shell. So what will we get?
linuxmint ~ # help ls bash: help: no help topics match `ls'. Try `help help' or `man -k ls' or `info ls'.
Next, I will try the
help command with the
cd command and you can see the result as shown below.
linuxmint ~ # help cd cd: cd [-L|[-P [-e]] [-@]] [dir] Change the shell working directory. Change the current directory to DIR. The default DIR is the value of the HOME shell variable. The variable CDPATH defines the search path for the directory containing DIR. Alternative directory names in CDPATH are separated by a colon (:). A null directory name is the same as the current directory. If DIR begins with a slash (/), then CDPATH is not used. If the directory is not found, and the shell option `cdable_vars' is set, the word is assumed to be a variable name. If that variable has a value, its value is used for DIR. Options: -L force symbolic links to be followed: resolve symbolic links in DIR after processing instances of `..' -P use the physical directory structure without following symbolic links: resolve symbolic links in DIR before processing instances of `..' -e if the -P option is supplied, and the current working directory cannot be determined successfully, exit with a non-zero status -@ on systems that support it, present a file with extended attributes as a directory containing the file attributes The default is to follow symbolic links, as if `-L' were specified. `..' is processed by removing the immediately previous pathname component back to a slash or the beginning of DIR. Exit Status: Returns 0 if the directory is changed, and if $PWD is set successfully when -P is used; non-zero otherwise.
Note: square brackets are displayed for the option of the command.
In the example with the cd command above, the options of the command with square brackets are
cd [-L|[-P [-e]] [-@]] [dir].
Display usage information with –help
In addition to using the
help command, most Linux commands support the
When you type the
--help syntax as shown below, the instruction manual of the command will be displayed.
$ command --help
For example, use the
--help option with the mkdir command.
linuxmint ~ # mkdir --help Usage: mkdir [OPTION]... DIRECTORY... Create the DIRECTORY(ies), if they do not already exist. Mandatory arguments to long options are mandatory for short options too. -m, --mode=MODE set file mode (as in chmod), not a=rwx - umask -p, --parents no error if existing, make parent directories as needed -v, --verbose print a message for each created directory -Z set SELinux security context of each created directory to the default type --context[=CTX] like -Z, or if CTX is specified then set the SELinux or SMACK security context to CTX --help display this help and exit --version output version information and exit GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/mkdir> or available locally via: info '(coreutils) mkdir invocation'
Tips: try typing
--help when you’re not sure how to use that command.
Through this article, you learned how to display usage information, displaying help information for Linux commands.If you liked this article, then please subscribe to our YouTube Channel for more video tutorials. You can also find us on Twitter and Facebook.
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