UNIX for Advanced & Expert Users

#include"headers.h"
static void sig_usr(int);
main()
{
        if(signal(SIGUSR1,sig_usr)==SIG_ERR)
                printf("cant catch signal sigusr1");
        if(signal(SIGUSR2,sig_usr)==SIG_ERR)
                printf("cant catch signal sigusr2");
        while(1);
        pause();
}
static void sig_usr(int signo)
{
if(signo==SIGUSR1)
        printf("Rx sigusr1");
else if(signo==SIGUSR2)
        printf("Rx sigusr2");
else printf("recieved signal is %d",signo);
return;
}

Breakpoint 1, main () at catch_signal.c:5
5       if(signal(SIGUSR1,sig_usr)==SIG_ERR)
(gdb) n
7       if(signal(SIGUSR2,sig_usr)==SIG_ERR)
(gdb) n
9       while(1);
(gdb) n

Program received signal SIGUSR1, User defined signal 1.
main () at catch_signal.c:9
9       while(1);
(gdb) n
sig_usr (signo=10) at catch_signal.c:13
13  {
(gdb) n
14  if(signo==SIGUSR1)
(gdb) n
15      printf("Rx sigusr1");
(gdb) n

Program received signal SIGTRAP, Trace/breakpoint trap.
0x08048326 in printf@plt ()
(gdb) n
Single stepping until exit from function printf@plt,
which has no line number information.
0x08048310 in ?? ()
(gdb) n
Cannot find bounds of current function

   signum   signame   Name            Description
   ___________________________________________________________________________
      0     SIGNULL   Null            Check access to pid
      1     SIGHUP    Hangup          Terminate; can be trapped
      2     SIGINT    Interrupt       Terminate; can be trapped
      3     SIGQUIT   Quit            Terminate with core dump; can be trapped
      9     SIGKILL   Kill            Forced termination; cannot be trapped
     15     SIGTERM   Terminate       Terminate; can be trapped
     24     SIGSTOP   Stop            Pause the process; cannot be trapped
     25     SIGTSTP   Terminal stop   Pause the process; can be trapped
     26     SIGCONT   Continue        Run a stopped process
 
signal.h:
 
/* Signal numbers */
#  define _SIGHUP       1       /* hangup */
#  define SIGINT        2       /* Interrupt */
#  define _SIGQUIT      3       /* quit */
#  define SIGILL        4       /* Illegal instruction (not reset when
                                   caught) */
#  define _SIGTRAP      5       /* trace trap (not reset when caught) */
#  define SIGABRT       6       /* Process abort signal */
#  define _SIGIOT       SIGABRT /* IOT instruction */
#  define _SIGEMT       7       /* EMT instruction */
#  define SIGFPE        8       /* Floating point exception */
#  define _SIGKILL      9       /* kill (cannot be caught of ignored) */
#  define _SIGBUS       10      /* bus error */
#  define SIGSEGV       11      /* Segmentation violation */
#  define _SIGSYS       12      /* bad argument to system call */
#  define _SIGPIPE      13      /* write on a pipe with no one to read it */
#  define _SIGALRM      14      /* alarm clock */
#  define SIGTERM       15      /* Software termination signal from kill */
#  define _SIGUSR1      16      /* user defined signal 1 */
#  define _SIGUSR2      17      /* user defined signal 2 */
#  define _SIGCHLD      18      /* Child process terminated or stopped */
#  define _SIGCLD       _SIGCHLD        /* death of a child */
#  define _SIGPWR       19      /* power state indication */
#  define _SIGVTALRM    20      /* virtual timer alarm */
#  define _SIGPROF      21      /* profiling timer alarm */
#  define _SIGIO        22      /* asynchronous I/O */
#  define _SIGPOLL      _SIGIO  /* for HP-UX hpstreams signal */
#  define _SIGWINCH     23      /* window size change signal */
#  define _SIGWINDOW    _SIGWINCH /* added for compatibility reasons */
#  define _SIGSTOP      24      /* Stop signal (cannot be caught or ignored) */
#  define _SIGTSTP      25      /* Interactive stop signal */
#  define _SIGCONT      26      /* Continue if stopped */
#  define _SIGTTIN      27      /* Read from control terminal attempted by a
                                   member of a background process group */
#  define _SIGTTOU      28      /* Write to control terminal attempted by a
                                   member of a background process group */
#  define _SIGURG       29      /* urgent condition on IO channel */
#  define _SIGLOST      30      /* remote lock lost  (NFS)        */
#  define _SIGRESERVE   31      /* Save for future use */
#  define _SIGDIL       32      /* DIL signal */
#  define _SIGXCPU      33      /* CPU time limit exceeded (setrlimit)  */
#  define _SIGXFSZ      34      /* CPU file size limit exceeded (setrlimit)  */
#  define _SIGCANCEL    35      /* Used for pthread cancellation. */
#  define _SIGGFAULT    36      /* Graphics framebuffer fault */
#  define _SIGRTMIN     37      /* First (highest priority) realtime signal */
#  define _SIGRTMAX     44      /* Last (lowest priority) realtime signal */