Member Avatar for zkjian517

when i read linux boot scripts, i often meet this expression: ${1:-}. i can't understand it. what's more, i don't understand this condition: [ -z "${1:-}" ] too. anyone can help me ? thanks!!!

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Member Avatar for vgersh99

When i read linux boot scripts, i often meet this expression: ${1:-}. i can't understand it. what's more, i don't understand this condition: [ -z "${1:-}" ] too. anyone can help me ? thanks!!!

 ${parameter:-word}
           Use Default Values. If parameter is unset or null,
           the  expansion of word will be substituted; other-
           wise, the value of parameter will be substituted.

 -z string True, if length of string is zero.
Edited by TrustyTony because: fixed formatting
Member Avatar for vgersh99

doing 'man ksh' yields:

${parameter:-word}
           Use Default Values. If parameter is unset or null,
           the  expansion of word will be substituted; other-
           wise, the value of parameter will be substituted.

 -z string True, if length of string is zero.
Edited by TrustyTony because: fixed formating
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