This subchapter looks at UNIX and Linux signals.
Teach Yourself UNIX/Linux System Administration and Shell Programming
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This subchapter looks at UNIX and Linux signals.
The first chart shows the signals by name, with their explanation and their numbers by operating system. The second chart shows the signals by number, with the corresponding name by operating system.
| name | meaning | Linux | Mac OS X | Solaris |
|---|---|---|---|---|
| SIGABRT | Used by abort | 6 create core image | 6 | |
| SIGALRM | Alarm clock, real-time timer expired (POSIX) | 14 | 14 terminate process | 14 |
| SIGBUS | BUS error (BSD 4.2) | 7 | 10 create core image | 10 |
| SIGCANCEL | Thread cancellation signal used by libthread | 36 | ||
| SIGCHLD | Child process has stopped or exited, Child status change alias (POSIX) | 17 | 20 discard signal | 18 |
| SIGCONT | Continue executing, if stopped; Stopped process has been continued (POSIX) | 18 | 19 discard signal | 25 |
| SIGEMT | EMT instruction; Emulate instruction executed | 7 create core image | 7 | |
| SIGFPE | Floating point exception (ANSI) | 8 | 8 create core image | 8 |
| SIGFREEZE | Special signal used by CPR | 34 | ||
| SIGHUP | Hangup (POSIX) | 1 | 1 terminate process | 1 |
| SIGILL | Illegal instruction (ANSI) | 4 | 4 create core image | 4 |
| SIGINFO | status request from keyboard | 29 terminate process | ||
| SIGINT | Terminal interrupt (ANSI) | 2 | 2 terminate process | 2 |
| SIGIO | I/O now possible (BSD 4.2) | 29 | 23 discard signal | 22 |
| SIGIOT | IOT Trap (BSD 4.2) | 6 | 6 create core image now called SIGABRT | |
| SIGKILL | Kill (POSIX) (can’t be caught or ignored) | 9 | 9 terminate process | 9 |
| SIGLOST | Resource lost | 37 | ||
| SIGLWP | Special signal used by thread library | 33 | ||
| SIGPIPE | Write on a pipe with no reader, Broken pipe (POSIX) | 13 | 13 terminate process | 13 |
| SIGPOLL | Pollable event occurred or Socket I/O possible | 22 | ||
| SIGPROF | Profiling alarm clock, profiling timer expired (BSD 4.2) | 27 | 27 terminate process | 29 |
| SIGPWR | Power failure restart (System V) | 30 | 19 | |
| SIGQUIT | Terminal quit (POSIX) | 3 | 3 create core image | 3 |
| SIGRTMAX | Lowest priority real-time signal | 45 | ||
| SIGRTMIN | Highest priority real-time signal | 38 | ||
| SIGSEGV | Invalid memory segment access, Segmentation violation (ANSI) | 11 | 11 create core image | 11 |
| SIGSTKFLT | Stack fault | 16 | ||
| SIGSTOP | Stop executing (POSIX) (can’t be caught or ignored) | 19 | 17 stop process | 23 |
| SIGSYS | Bad argument to system call; Non-existent system call invoked | 12 create core image | 12 | |
| SIGTERM | Software termination (ANSI) | 15 | 15 terminate process | 15 |
| SIGTHAW | Special signal used by CPR | 35 | ||
| SIGTRAP | Trace trap (POSIX) | 5 | 5 create core image | 5 |
| SIGTSTP | Terminal stop signal, User stop requested from TTY (POSIX) | 20 | 18 stop process | 24 |
| SIGTTIN | Background process trying to read from TTY control terminal (POSIX) | 21 | 21 stop process | 26 |
| SIGTTOU | background process trying to write to TTY control terminal (POSIX) | 22 | 22 stop process | 27 |
| SIGURG | Urgent condition on socket (BSD 4.2) | 23 | 16 discard signal | 21 |
| SIGUSR1 | User defined signal 1 (POSIX) | 10 | 30 terminate process | 16 |
| SIGUSR2 | User defined signal 2 (POSIX) | 12 | 31 terminate process | 17 |
| SIGVTALRM | Virtual alarm clock, Virtual timer expired (BSD 4.2) | 26 | 26 terminate process | 28 |
| SIGWAITING | Process’ LWPs are blocked | 32 | ||
| SIGWINCH | Window size change (BSD 4.3, Sun) | 28 | 28 discard signal | 20 |
| SIGXCPU | CPU limit exceeded (BSD 4.2) | 24 | 24 terminate process | 30 |
| SIGXFSZ | File size limit exceeded (BSD 4.2) | 25 | 25 terminate process | 31 |
| number | Linux | Mac OS X | Solaris |
|---|---|---|---|
| 1 | SIGHUP | SIGHUP | SIGHUP |
| 2 | SIGINT | SIGINT | SIGINT |
| 3 | SIGQUIT | SIGQUIT | SIGQUIT |
| 4 | SIGILL | SIGILL | SIGILL |
| 5 | SIGTRAP | SIGTRAP | SIGTRAP |
| 6 | SIGIOT | SIGABRT | SIGABRT |
| 7 | SIGBUS | SIGEMT | SIGEMT |
| 8 | SIGFPE | SIGFPE | SIGFPE |
| 9 | SIGKILL | SIGKILL | SIGKILL |
| 10 | SIGUSR1 | SIGBUS | SIGBUS |
| 11 | SIGSEGV | SIGSEGV | SIGSEGV |
| 12 | SIGUSR2 | SIGSYS | SIGSYS |
| 13 | SIGPIPE | SIGPIPE | SIGPIPE |
| 14 | SIGALRM | SIGALRM | SIGALRM |
| 15 | SIGTERM | SIGTERM | SIGTERM |
| 16 | SIGSTKFLT | SIGURG | SIGUSR1 |
| 17 | SIGCHLD | SIGSTOP | SIGUSR2 |
| 18 | SIGCONT | SIGTSTP | SIGCHLD |
| 19 | SIGSTOP | SIGCONT | SIGPWR |
| 20 | SIGTSTP | SIGCHLD | SIGWINCH |
| 21 | SIGTTIN | SIGTTIN | SIGURG |
| 22 | SIGTTOU | SIGTTOU | SIGIO SIGPOLL |
| 23 | SIGURG | SIGIO | SIGSTOP |
| 24 | SIGXCPU | SIGXCPU | SIGTSTP |
| 25 | SIGXFSZ | SIGXFSZ | SIGCONT |
| 26 | SIGVTALRM | SIGVTALRM | SIGTTIN |
| 27 | SIGPROF | SIGPROF | SIGTTOU |
| 28 | SIGWINCH | SIGWINCH | SIGVTALRM |
| 29 | SIGIO | SIGINFO | SIGPROF |
| 30 | SIGPWR | SIGUSR1 | SIGXCPU |
| 31 | SIGUSR2 | SIGXFSZ | |
| 32 | SIGWAITING | ||
| 33 | SIGLWP | ||
| 34 | SIGFREEZE | ||
| 35 | SIGTHAW | ||
| 36 | SIGCANCEL | ||
| 37 | SIGLOST | ||
| 38 | SIGRTMIN | ||
| 45 | SIGRTMAX |
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Created: November 20, 2012
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