What does thecolon minus do in a shell?
时间：2010-09-10 来源：bigluo
Q: I am looking at a script written for the runscript shell. I have a line as
follows:
if [[ ${RC_INTERACTIVE:-yes} == "yes" ]] ; then
I would like to know what the :- (colon minus) operator that follows the
variable name does.
A: Like in a normal (POSIX like) shell - "info bash" says:
${PARAMETER:-WORD}'
If PARAMETER is unset or null, the expansion of WORD is
substituted. Otherwise, the value of PARAMETER is substituted.
follows:
if [[ ${RC_INTERACTIVE:-yes} == "yes" ]] ; then
I would like to know what the :- (colon minus) operator that follows the
variable name does.
A: Like in a normal (POSIX like) shell - "info bash" says:
${PARAMETER:-WORD}'
If PARAMETER is unset or null, the expansion of WORD is
substituted. Otherwise, the value of PARAMETER is substituted.
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