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Linux使用 -- 脚本控制
source link: http://zhongmingmao.me/2019/10/20/linux-practice-shell-control/
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- 使用 nice 和 renice 来调整脚本优先级
- 避免出现不可控的 死循环 （导致 CPU占用过高 或 死机 ）
Fork炸弹
# 大部分限制对root无效 [root@localhost ~]# ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 3795 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 3795 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
Session A
[zhongmingmao@localhost ~]$ func() {
> func | func&
> }
[zhongmingmao@localhost ~]$ func
-bash: fork: retry: No child processes
-bash: fork: retry: No child processes
...
-bash: fork: Resource temporarily unavailable
-bash: fork: Resource temporarily unavailable
Session B
load很高
[root@localhost ~]# id zhongmingmao uid=1000(zhongmingmao) gid=1000(zhongmingmao) 组=1000(zhongmingmao) [root@localhost ~]# top -u 1000 top - 22:26:34 up 5:49, 3 users, load average: 337.21, 175.05, 74.72 Tasks: 107 total, 1 running, 106 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.0 us, 0.3 sy, 0.0 ni, 99.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 995748 total, 840952 free, 105932 used, 48864 buff/cache KiB Swap: 2097148 total, 2013948 free, 83200 used. 793856 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 5012 zhongmi+ 20 0 115580 820 800 S 0.0 0.1 0:00.05 bash [root@localhost ~]# kill -9 5012
捕获信号
- kill 默认会发送 15 号信号给应用程序
- ctrl+c 发送 2 号信号给应用程序
- 9号信号不可阻塞！！
[root@localhost ~]# kill -l 1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT 17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP 21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN 35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3 38) SIGRTMIN+4 39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8 43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6 59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2 63) SIGRTMAX-1 64) SIGRTMAX
[root@localhost ~]# cat 15.sh
#!/bin/bash
trap "echo sig 15" 15
trap "echo sig 2" 2
echo $$
while :
do
:
done
Session A
[root@localhost ~]# bash 15.sh 17560
Session B
[root@localhost ~]# kill 17560
Session A
程序不会结束
[root@localhost ~]# bash 15.sh 17560 sig 15
Session B
[root@localhost ~]# kill -9 17560
Session A
程序结束
[root@localhost ~]# bash 15.sh 17560 sig 15 已杀死
ctrl+c也无法结束程序
[root@localhost ~]# bash 15.sh 17608 ^Csig 2
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