Unix Tip: Filename completion

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A number of readers have recently asked how they set up and use filename completion in a variety of Unix shells. Since file completion does not work the same in every shell, we will examine how you can use this great time saving feature in csh (tcsh), bash and ksh.

csh



The C Shell implements file completion in the most straightforward and easy-to-use manner. When the filec environment variable is set (using a "set filec" command), all you have to do is type the leftmost part of a filename and then press the Escape key. The shell will fill in the remainder of the file name or as much of the filename as can be filled in before a choice must be made between a number of files starting with the same substring. For example, if a user were to type "more pro" and then press Escape, the system might fill in "gram" and then wait for the user to type 1 or 2. If the files in the current directory include a file named program1.c, one called program2.c and another called program3.c, entering a 1, 2 or a 3 and then pressing Escape again will yield the full name of the file. The "set filec" command is generally put in one of the user's startup files (e.g., ~/.cshrc) so that the user doesn't need to remember to type it on the command line whenever he logs in or opens a new window.

If, for some unfathomable reason, you decide to turn this feature off, all you have to do is "unset" filec with the, unsurprising, "unset filec" command and pressing escape will no longer function as was just described.

bash

Bash also provides filename completion, but it uses a tab instead of an Escape character to invoke the file completion operation. However, bash doesn't require you to set an environment variable; it just provides file completion by default. Bash also implements an additional filename completion feature. If, after typing a portion of a filename and then pressing tab, you reach that point at which multiple files satisfy your request and you need to add more text to select one of the files, you can press tab twice more for a list of the files that match what you have typed thus far.

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