Iterating over a list of possible signals

Question

I have some code that I want to use to print a list of signals that prints the names of the signals in the signal mask of the calling process.

The starting code that I h

Answer 1

Create a structure type, and preload an array with the appropriate information:

struct SigInfo
{
    int     signum;
    char    signame[16];
};

static const struct SigInfo siginfo[] =
{
#ifdef SIGINT
        { SIGINT, "SIGINT" },
#endif
#ifdef SIGQUIT
        { SIGQUIT, "SIGQUIT" },
#endif
    …
};
enum { NUM_SIGINFO = sizeof(siginfo) / sizeof(siginfo[0]) };

And then:

printf("%s", str); 
for (int i = 0; i < NUM_SIGINFO; i++)
{
    if (sigismember(&sigset, siginfo[i].signum))
    {
        printf(" %s\n", siginfo[i].signame);
        break;
    }
}

You can package the information multiple different ways. Generating the signal information is fiddly. I use a Perl script to scrutinize the appropriate header (usually /usr/include/sys/errno.h) and extract the information shown, plus the text of what the signal is for, plus the number associated with the signal:

typedef struct sig_info
{
    const char *sigsym;     /* Signal symbol  - "EINTR" */
    int         signum;     /* Signal number  - EINTR   */
    int         sigdef;     /* Signal define  - 2       */
    const char *sigmsg;     /* Signal message - Interrupted system call */
} sig_info;

…
#ifdef SIGPIPE
    {   "SIGPIPE",   SIGPIPE,   13,   "Broken pipe (POSIX)."                  },
#endif
#ifdef SIGPROF
    {   "SIGPROF",   SIGPROF,   27,   "Profiling alarm clock (4.2 BSD)."      },
#endif
#ifdef SIGPWR
    {   "SIGPWR",    SIGPWR,    30,   "Power failure restart (System V)."     },
#endif
…

The program this comes from allows me to find signals by name or number:

$ ./signal int 2
SIGINT (2): Interrupt (ANSI).
2 (SIGINT): Interrupt (ANSI).
$ ./signal -h
Usage: signal [-hlqV] [lo[:hi] ...]
  -h    Print help and exit
  -l    Print list of all signals
  -q    Validate signal but don't print messages
  -V    Print version and exit
$ ./signal -l
1 (SIGHUP): Hangup (POSIX).
2 (SIGINT): Interrupt (ANSI).
3 (SIGQUIT): Quit (POSIX).
4 (SIGILL): Illegal instruction (ANSI).
5 (SIGTRAP): Trace trap (POSIX).
6 (SIGIOT): IOT trap (4.2 BSD).
6 (SIGIOT): IOT trap (4.2 BSD).
7 (SIGBUS): BUS error (4.2 BSD).
8 (SIGFPE): Floating-point exception (ANSI).
9 (SIGKILL): Kill, unblockable (POSIX).
10 (SIGUSR1): User-defined signal 1 (POSIX).
11 (SIGSEGV): Segmentation violation (ANSI).
12 (SIGUSR2): User-defined signal 2 (POSIX).
13 (SIGPIPE): Broken pipe (POSIX).
14 (SIGALRM): Alarm clock (POSIX).
15 (SIGTERM): Termination (ANSI).
16 (SIGSTKFLT): Stack fault.
17 (SIGCHLD): Child status has changed (POSIX).
18 (SIGCONT): Continue (POSIX).
19 (SIGSTOP): Stop, unblockable (POSIX).
20 (SIGTSTP): Keyboard stop (POSIX).
21 (SIGTTIN): Background read from tty (POSIX).
22 (SIGTTOU): Background write to tty (POSIX).
23 (SIGURG): Urgent condition on socket (4.2 BSD).
24 (SIGXCPU): CPU limit exceeded (4.2 BSD).
25 (SIGXFSZ): File size limit exceeded (4.2 BSD).
26 (SIGVTALRM): Virtual alarm clock (4.2 BSD).
27 (SIGPROF): Profiling alarm clock (4.2 BSD).
28 (SIGWINCH): Window size change (4.3 BSD, Sun).
29 (SIGIO): I/O now possible (4.2 BSD).
30 (SIGPWR): Power failure restart (System V).
31 (SIGSYS): Bad system call.
34 (SIGRT34): Real time signal 34 (SIGRTMIN)
35 (SIGRT35): Real time signal 35
…
63 (SIGRT63): Real time signal 63
64 (SIGRT64): Real time signal 64 (SIGRTMAX)
$

This particular list of signals was generated on an ancient RedHat Linux machine (5.2, IIRC). The effect is similar on macOS, and other versions of Linux too.