Variables
This subsection describes the following:
Variable substitution
Variable modifiers
Predefined shell variables
Formatting for the prompt variable
Sample .tcshrc file
Environment variables
Variable Substitution
In the following substitutions, braces ({ }) are optional, except when needed to separate a variable name from following characters that would otherwise be considered part of the name.
Variable |
Description |
---|---|
${ var } |
The value of variable var. |
${ var [ i ]} |
Select word or words in position i of var. i can be a single number, a range m-n, a range -n (missing m implies 1), a range m- (missing n implies all remaining words), or * (select all words). i also can be a variable that expands to one of these values. |
${# var } |
The number of words in var. |
${#argv} |
The number of arguments. |
$0 |
Name of the program. |
${argv[ n ]} |
Individual arguments on command line (positional parameters); 1 ≤ n ≤ 9. |
${n} |
Same as ${argv[ n ]}. |
${argv[*]} |
All arguments on command line. |
$* |
Same as {$argv[*]}. |
$argv[$#argv] |
The last argument. |
${? var } |
Return 1 if var is set, 0 if not. |
$$ |
Process number of current shell; useful as part of a filename for creating temporary files with unique names. |
${? name } |
Return 1 if name is set, 0 if not. |
$?0 |
Return 1 if input filename is known, 0 if not. |
Examples
Sort the third through last arguments and save the output in a file whose name is unique to this process:
sort $argv[3-] > tmp.$$
Process .tcshrc commands ...
Get Linux in a Nutshell, Fourth Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.