Linux Signals

A signal is a limited form of inter-process communication used in Unix, Unix-like (Linux), and other POSIX-compliant operating systems.

The Single Unix Specification specifies the following signals which are defined in :

SIGABRT - process aborted 
SIGALRM - signal raised by alarm 
SIGBUS - bus error: "access to undefined portion of memory object" 
SIGCHLD - child process terminated, stopped (*or continued) 
SIGCONT - continue if stopped 
SIGFPE - floating point exception: "erroneous arithmetic operation" 
SIGHUP - hangup 
SIGILL - illegal instruction 
SIGINT - interrupt 
SIGKILL - kill 
SIGPIPE - write to pipe with no one reading 
SIGQUIT - quit 
SIGSEGV - segmentation violation 
SIGSTOP - stop executing temporarily 
SIGTERM - termination 
SIGTSTP - terminal stop signal 
SIGTTIN - background process attempting to read ("in") 
SIGTTOU - background process attempting to write ("out") 
SIGUSR1 - user defined 1 
SIGUSR2 - user defined 2 
*SIGPOLL - pollable event 
*SIGPROF - profiling timer expired 
*SIGSYS - bad syscall 
*SIGTRAP - trace/breakpoint trap 
SIGURG - urgent data available on socket 
*SIGVTALRM - signal raised by timer counting virtual time: "virtual timer expired" 
*SIGXCPU - CPU time limit exceeded 
*SIGXFSZ - file size limit exceeded 

To find the signals applicable on your distributions use the trap -l command, which yields output similar to that shown:

$ trap -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     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
$

Useful Links

For further information see the following links. For the full story consult the manual (man) pages for your distribution.