First the signals described in the original POSIX.1-1990 standard.

SIGHUP1TermHangup detected on controlling terminal or death of controlling process
SIGINT2TermInterrupt from keyboard
SIGQUIT3CoreQuit from keyboard
SIGILL4CoreIllegal Instruction
SIGABRT6CoreAbort signal from abort(3)
SIGFPE8CoreFloating point exception
SIGKILL9TermKill signal
SIGSEGV11CoreInvalid memory reference
SIGPIPE13TermBroken pipe: write to pipe with no readers
SIGALRM14TermTimer signal from alarm(2)
SIGTERM15TermTermination signal
SIGUSR130,10,16TermUser-defined signal 1
SIGUSR231,12,17TermUser-defined signal 2
SIGCHLD20,17,18IgnChild stopped or terminated
SIGCONT19,18,25ContContinue if stopped
SIGSTOP17,19,23StopStop process
SIGTSTP18,20,24Stoptyped at terminal
SIGTTIN21,21,26StopTerminal input for background process
SIGTTOU22,22,27StopTerminal output for background process
The signals SIGKILL and SIGSTOP cannot be caught, blocked, or ignored.
Next the signals not in the POSIX.1-1990 standard but described in
SUSv2 and POSIX.1-2001.
SIGBUS10,7,10CoreBus error (bad memory access)
SIGPOLLTermPollable event (Sys V). Synonym for SIGIO
SIGPROF27,27,29TermProfiling timer expired
SIGSYS12,31,12CoreBad argument to routine (SVr4)
SIGTRAP5CoreTrace/breakpoint trap
SIGURG16,23,21IgnUrgent condition on socket (4.2BSD)
SIGVTALRM26,26,28TermVirtual alarm clock (4.2BSD)
SIGXCPU24,24,30CoreCPU time limit exceeded (4.2BSD)
SIGXFSZ25,25,31CoreFile size limit exceeded (4.2BSD)
Up to and including Linux 2.2, the default behavior for SIGSYS, SIGX‐CPU, SIGXFSZ, and (on architectures other than SPARC and MIPS) SIGBUS was to terminate the process (without a core dump). (On some other UNIX systems the default action for SIGXCPU and SIGXFSZ is to terminate the process without a core dump.) Linux 2.4 conforms to the POSIX.1-2001 requirements for these signals, terminating the process with a core dump.

Next various other signals.

SIGIOT6CoreIOT trap. A synonym for SIGABRT
SIGSTKFLT-,16,-TermStack fault on coprocessor (unused)
SIGIO23,29,22TermI/O now possible (4.2BSD)
SIGCLD-,-,18IgnA synonym for SIGCHLD
SIGPWR29,30,19TermPower failure (System V)
SIGINFO29,-,-A synonym for SIGPWR
SIGLOST-,-,-TermFile lock lost (unused)
SIGWINCH28,28,20IgnWindow resize signal (4.3BSD, Sun)
SIGUNUSED-,31,-CoreSynonymous with SIGSYS
(Signal 29 is SIGINFO / SIGPWR on an alpha but SIGLOST on a sparc.)

SIGEMT is not specified in POSIX.1-2001, but nevertheless appears on most other UNIX systems, where its default action is typically to ter‐ minate the process with a core dump.

SIGPWR (which is not specified in POSIX.1-2001) is typically ignored by default on those other UNIX systems where it appears.

SIGIO (which is not specified in POSIX.1-2001) is ignored by default on several other UNIX systems.

Where defined, SIGUNUSED is synonymous with SIGSYS on most architec‐ tures.