-I interruptible option is used to handle signals. The interruptible's value can be 1 ~ 4:
| Value | Meaning |
|---|---|
| 1 | Don't block any signal |
| 2 | Block fatal signals while decoding syscall, and this is default behaviour. |
| 3 | Block fatal signals, and this is default behaviour when using '-o FILE PROG' option. |
| 4 | Block fatal signals and SIGTSTP (^Z), and this is useful when not want '-o FILE PROG' option to stop on ^Z. |
The fatal signals include SIGHUP, SIGINT, SIGQUIT, SIGPIPE and SIGTERM. Check following example:
# strace -I 1 ./dead_loop
......
nanosleep({tv_sec=1, tv_nsec=0}, 0x7fff0a0d90f0) = 0
nanosleep({tv_sec=1, tv_nsec=0}, 0x7fff0a0d90f0) = 0
nanosleep({tv_sec=1, tv_nsec=0}, 0x7fff0a0d90f0) = 0
......
Open another terminal and input following command:
# kill -s INT `pidof strace`
You will find strace process is killed. If you run strace using "-I 3", you will find the SIGINT will not take effect when using above command:
# kill -s INT `pidof strace`