**Table of Contents** *generated with [DocToc](https://github.com/thlorenz/doctoc)* - [8 Command Execution](#8-command-execution) # 8 Command Execution If a command name contains no slashes, the shell attempts to locate it. If there exists a shell function by that name, the function is invoked as described in [Functions](Functions.html#Functions). If there exists a shell builtin by that name, the builtin is invoked. Otherwise, the shell searches each element of `$path` for a search is unsuccessful, the shell prints an error message and returns a nonzero exit status. and the file is not a directory, it is assumed to be a shell script. `/bin/sh` is spawned to execute it. If the program is a file beginning with ‘`#!`’, the remainder of the first line specifies an interpreter for the program. The shell will execute the specified interpreter on operating systems that do If no external command is found but a function `command_not_found_handler` exists the shell executes this function with all command line arguments. The return status of the function becomes the status of the command. If the function wishes to mimic the behaviour of the shell when the command is not found, it should print the message ‘`command not found:` `cmd`’ to standard error and return status 127. Note that the handler is executed in a subshell forked to execute an external command, hence changes to directories, shell parameters, etc. have no effect on the main shell. ----- This document was generated on *February 15, 2020* using [*texi2html 5.0*](http://www.nongnu.org/texi2html/). Zsh version 5.8, released on February 14, 2020.