Symbolic constants for signal numbers are typically defined in a header file: signal.h

Operating systems that are compliant with the POSIX standard must include the following names (associated numbers might be different on different systems.)

Here are the integers for one Linux system (Ubuntu):

#define SIGHUP          1       /* Hangup (POSIX).  */
#define SIGINT          2       /* Interrupt (ANSI).  */
#define SIGQUIT         3       /* Quit (POSIX).  */
#define SIGILL          4       /* Illegal instruction (ANSI).  */
#define SIGTRAP         5       /* Trace trap (POSIX).  */
#define SIGABRT         6       /* Abort (ANSI).  */
#define SIGIOT          6       /* IOT trap (4.2 BSDES).  */
#define SIGBUS          7       /* BUS error (4.2 BSD).  */
#define SIGFPE          8       /* Floating-point exception (ANSI).
#*/
#define SIGKILL         9       /* Kill, unblockable (POSIX).  */
#define SIGUSR1         10      /* User-defined signal 1 (POSIX).  */
#define SIGSEGV         11      /* Segmentation violation (ANSI).  */
#define SIGUSR2         12      /* User-defined signal 2 (POSIX).  */
#define SIGPIPE         13      /* Broken pipe (POSIX).  */
#define SIGALRM         14      /* Alarm clock (POSIX).  */
#define SIGTERM         15      /* Termination (ANSI).  */
#define SIGSTKFLT       16      /* Stack fault.  */
#define SIGCLD          SIGCHLD /* Same as SIGCHLD (System V).  */
#define SIGCHLD         17      /* Child status has changed (POSIX).
#*/
#define SIGCONT         18      /* Continue (POSIX).  */
#define SIGSTOP         19      /* Stop, unblockable (POSIX).  */
#define SIGTSTP         20      /* Keyboard stop (POSIX).  */
#define SIGTTIN         21      /* Background read from tty (POSIX).
#*/
#define SIGTTOU         22      /* Background write to tty (POSIX).
#*/
#define SIGURG          23      /* Urgent condition on socket (4.2
#BSD).  */
#define SIGXCPU         24      /* CPU limit exceeded (4.2 BSD).  */
#define SIGXFSZ         25      /* File size limit exceeded (4.2
#BSD).  */
#define SIGVTALRM       26      /* Virtual alarm clock (4.2 BSD).  */
#define SIGPROF         27      /* Profiling alarm clock (4.2 BSD).
#*/
#define SIGWINCH        28      /* Window size change (4.3 BSD, Sun).
#*/
#define SIGPOLL         SIGIO   /* Pollable event occurred (System
#V).  */
#define SIGIO           29      /* I/O now possible (4.2 BSD).  */
#define SIGPWR          30      /* Power failure restart (System V).
#*/
#define SIGSYS          31      /* Bad system call.  */
#define SIGUNUSED       31