Entering commands not in the PATH

Occasionally, you will need to execute a command that is not in your path and not built into your shell. If this need arises often, it may be best to simply add the directory that contains the command to your path. However, there’s nothing wrong with explicitly specifying a command’s location and name completely. For example, the ls command is located in /bin. This directory is most certainly in your PATH variable (if not, it should be!), which allows you to enter the ls command by itself on the command line:

$ ls

The shell looks for an executable file named ls in each successive directory listed in your PATH variable and will execute the first one it finds. Specifying the literal pathname for the command eliminates the directory search and yields identical results:

$ /bin/ls

Any executable file on your system may be started in this way. However, it is important to remember that some programs may have requirements during execution about what is listed in your PATH. A program can be launched normally but may fail if it is unable to find a required resource due to an incomplete PATH.

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