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"$!"是什么东西....?
一个守护进程脚本....
- #!/bin/sh
- if [ $# -lt 1 ] ; then
- echo "USAGE: &basename $0& command."
- Exit 0
- fi
- Init() {
- printf "INFO: Initializing... "
- # check if the last backgrounded pid is valid, if it is
- # try an kill it.
- kill -0 $! 2> /dev/null;
- if [ $? -eq 0 ] ; then
- kill $! > /dev/null 2>&1
- if [ $? -ne 0 ] ; then
- echo "ERROR: Already running as pid $!. Exiting."
- exit 1
- fi
- fi
- # start a new program in the background
- $PROG &
- printf "Done.\n"
- }
- CleanUp() {
- kill -9 $! ; exit 2 ;
- }
- # main()
- trap CleanUp 2 3 15
- trap Init 1
- PROG=$1
- Init
- while : ;
- do
- wait $!
- $PROG &
- done
复制代码
不知道什么是$! |
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