sorry in advance if stupid question, but i am a really new bie.
i found the following shell script in the configure file of autoconf-2.59
but dose that means ?
15 if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
16 emulate sh
17 NULLCMD=:
18 # Zsh 3.x and 4.x performs word splitting on ${1+"$@"}, which
19 # is contrary to our usage. Disable this feature.
20 alias -g '${1+"$@"}'='"$@"'
21 elif test -n "${BASH_VERSION+set}" && (set -o posix)
>/dev/null 2>&1; then
22 set -o posix
23 fi
i know ${ZSH_VERSION} means variable substituting;
and ${ZSH_VERSION:+set} means "If parameter is null or unset, nothing
~~ Note the `:`
is substituted, otherwise the expansion of word is substituted."
---- from Bash reference manual
but what dose ${ZSH_VERSION+set} without the `:` means ?
thanks in advance.
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