C Shell Scripting/Parameters

Passing parameters to a script In scripts, the variables $0, $1, $2, and so on are known as positional parameters. The variable $0 refers to the name of the command and $1, $2 and greater will be the parameters passed into the script. When a csh script is invoked, the special variable argv is set to the wordlist of arguments given on the command line. Thus, as alternatives to the special variables $1, $2 and so on, csh scripts can use $argv[1], $argv[2], and so on to access command line arguments. The value of the variable $#argv is the number of arguments given. For example write a myparams script: #!/bin/csh -f echo The $0 command is called with $#argv parameters echo parameter 1 is $1 echo parameter 2 is $2 echo parameter 3 is $3 echo parameter 4 is $4 echo 2nd and on parameters are \"$argv[2-]\" echo All Parameters are \"$argv\" echo All Parameters are \"$argv[*]\" echo All Parameters are \"$*\" then run the command: ./myparams alpha beta omega This prints out the following: The ./myparams command is called with 3 parameters parameter 1 is alpha parameter 2 is beta parameter 3 is omega parameter 4 is All Parameters are "alpha beta omega" 2nd and on parameters are "beta omega" If the parameter is missing the value of the position parameter will be a blank string as is the case of the 4th parameter. Also, you can get the entire or part of the command-line using the variable $argv which is a wordlist. If you want to include spaces in a single parameter you must quote the value. For example running this command: ./myparams "alpha beta" omega would print out the following: The ./myparams command is called with 2 parameters parameter 1 is alpha beta parameter 2 is omega parameter 3 is parameter 4 is All Parameters are "alpha beta omega" 2nd and on parameters are "omega" The alpha and beta value are now combined as a single value. Lessons Parameters passed to a script are accessible using numbered variables like $1, $2, $3 and so on. Parameters passed to a script are also accessible using wordlist variable called $argv