这个bash参数扩展语法的含义是什么？

Question

In the golang GOPATH documentation it instructs you to add the following to your bash PATH:

${GOPATH//://bin:}/bin

What does the //://bin: mean here?

$GOPATH appears to evaluate to the same value as ${GOPATH//://bin:}

My first guess was that this somehow expands into all subdirectories of $GOPATH that have a /bin subdirectory, but this does not appear to be the case. I added some subdirectories to my $GOPATH with a /bin dir, and the above expression does not include them.

I dug into my manpage for bash and didn't see any hints.

Answer 1

man bash says under PARAMETER EXPANSION:

${parameter/pattern/string}

Pattern substitution. The pattern is expanded to produce a pattern just as in pathname expansion. Parameter is expanded and the longest match of pattern against its value is replaced with string. If pattern begins with /, all matches of pattern are replaced with string. Normally only the first match is replaced.

eg

$ GOPATH=a:b:c
$ echo ${GOPATH//://bin:}
a/bin:b/bin:c