9.3 Standard shell commands

The standard shell commands are divided into special built-in commands and regular built-in commands, as shown below. A built-in command is one that is included as part of the shell, and is executed by the shell itself.

• Special built-in commands

  If a special built-in command's syntax is invalid, it exits the shell that is executing the command.

• Regular built-in commands

  Even if a regular built-in command's syntax is invalid, it does not exit the shell that is executing the command.

Organization of this section

• . command (executes a shell script)

• : command (expands arguments)

• alias command (defines aliases)

• break command (exits from a loop)

• builtin command (executes a built-in command)

• cd command (changes the current directory)

• command command (executes a command)

• continue command (interrupts loop processing and returns to the beginning of the loop)

• echo command (outputs what is specified in arguments to the standard output)

• eval command (concatenates arguments into a command and executes it)

• exec command (executes a command and exits)

• exit command (exits the shell)

• export command (exports shell variables)

• false command (returns 1 as the return code)

• getopts command (parses option arguments)

• kill command (sends a signal)

• let command (evaluates the values of arithmetic expressions)

• print command (outputs to the standard output)

• pwd command (outputs the path of the current directory)

• read command (reads from the standard input and stores the input in variables)

• readonly command (sets the read-only attribute for variables or displays all read-only variables)

• return command (returns from a function or an external script)

• set command (sets shell options, creates an array, or displays variable values)

• shift command (shifts the run-time parameters)

• test command (determines the value of a conditional expression)

• times command (displays the amount of CPU time used by the shell)

• trap command (specifies the action when signals and forced termination requests are received)

• true command (returns 0 as the return code)

• typeset command (declares explicitly the attributes and values of variables and functions)

• ulimit command (sets limits on system resources) (UNIX only)

• umask command (sets the access permissions for creating a new file) (UNIX only)

• unalias command (removes alias definitions)

• unset command (unsets variable values and attributes)

• wait command (waits for child processes to complete)

• whence command (displays how character strings would be interpreted if used as commands)

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