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2003/09/24 argument, args


© September 2003 Tony Lawrence

A value passed to a program. Abbreviated to args, but usually only in the plural. It's fairly common to specifically say "command line arguments". Arguments read from a file are often referred to as "parameters" rather than arguments. Flags (also "switches") are a type of argument, almost always prefaced by some character that tells you that: typically a "-" in Unix and Linux, and a "/" (the "switch character") in the Windows world. So, in

sort -u /tmp/file
 

most geekish types would say that "-u" (sort uniquely) is a flag, and /tmp/file is an argument. But remember that a flag is a type of argument; "/tmp/file" would never be a flag, but "-u" will be called an argument in some contexts.

A very few Unix programs process flags with or without the lead-in character: both "tar tvf /dev/rct0" and "tar -tvf /dev/rct0" are acceptable.

Most Unix programs will accept file arguments or read from standard input: you can "cat file | sort" or "sort file" with equal results.

Unix shells are responsible for expanding wild-cards and passing the result to the program that will use them. So when you say

cp x* /tmp
 

"cp" sees all the "x" files; it does not see "x*".

Sometimes you don't want the shell expansion of wildcards. Using "find -name x*" will fail if there are any files named "x*" in the current directory. You need to "find -name 'x*'" so that find gets the actual wildcard to work with.


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