#1 Finding Programs in the PATH

Shell scripts that use environment variables (like MAILER and PAGER) have a hidden danger: Some of their settings may well point to nonexistent programs. For example, if you decide to be flexible by using the PAGER setting to display script output, instead of just hard-coding a specific tool, how do you ensure that the PAGER value is set to a valid program? After all, if it's not a valid program, your script will break. This first script addresses how to test whether a given program can be found in the user's PATH, and it's also a good demonstration of a number of different shell scripting techniques, including script functions and variable slicing.

The Code

 #!/bin/sh # inpath - Verifies that a specified program ...

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