Chris's Wiki :: blog/unix/ShellImportanceOfASpace

In the sidebar to yesterday's entry I (originally) made a Unix command line mistake by unthinkingly leaving out an ordinary, innocent looking space (it's corrected in the current version of the entry after it was noted by Emilio in a comment). This innocent looking mistake and its consequences are an illustration of something in Unix shell command lines, although I'm not sure of just what, so I'm going to write it up.

read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name …]

The 'read' builtin follows the general standard behavior of Unix commands where '-d delim' and other options that take an argument can be shortened to omit the space, so '-ddelim'. So you can write, for example:

Bash also has a special feature for -d. Normally the first character of delim is taken as the 'line' terminator, but if delim is blank, read will terminate the line when it reads a NUL character (0 byte), which is just what you want to handle the output of, for example, 'find ... -print0'.

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