Command parameters

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After the command name, there might be a number of flags, followed by parameters. Parameters are sometimes called arguments or operands. Parameters specify information that the command needs in order to run.

If you do not specify a parameter, the command might assume a default value. For example, in the following command:

ls -a temp

ls is the command name, -a is the flag, and temp is the parameter. This command displays all (-a) the files in the directory temp.

In the following example:

ls -a

the default value is the current directory because no parameter is given.

In the following example:

ls temp mail

no flags are given, and temp and mail are parameters. In this case, temp and mail are two different directory names. The ls command displays all but the hidden files in each of these directories.

Whenever a parameter or option-argument is, or contains, a numeric value, the number is interpreted as a decimal integer, unless otherwise specified. Numerals in the range 0 to INT_MAX, as defined in the /usr/include/sys/limits.h file, are syntactically recognized as numeric values.

If a command you want to use accepts negative numbers as parameters or option-arguments, you can use numerals in the range INT_MIN to INT_MAX, both as defined in the /usr/include/sys/limits.h file. This does not necessarily mean that all numbers within that range are semantically correct. Some commands have a built-in specification permitting a smaller range of numbers, for example, some of the print commands. If an error is generated, the error message lets you know the value is out of the supported range, not that the command is syntactically incorrect.