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Bash - Special variables

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Wednesday, 10 August 2011 15:04
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Bash special variables explained

Bash Special variables

The following table describes the variables you can use in your Bash scipt and the meaning associtated.

Special Shell Variables

VariableDescription
$0 Filename of script
$1 Positional parameter #1
$2 - $9 Positional parameters #2 - #9
${10} Positional parameter #10
$# Number of positional parameters
"$*" All the positional parameters (as a single word) *
"$@" All the positional parameters (as separate strings)
${#*} Number of positional parameters
${#@} Number of positional parameters
$? Return value
$$ Process ID (PID) of script
$- Flags passed to script (using set)
$_ Last argument of previous command
$! Process ID (PID) of last job run in background

* Must be quoted, otherwise it defaults to "$@".

On the same subject you can consule the article about the Bash File test operators

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Tags: process, parameters, positional, special, number, script, variables, bash, parameter, argument

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