C语言 信号编号到名称

Question

如何从号码中快速获取信号名称?有strsignal()，但我只想要名称，例如SIGUSR1

换句话说，如果我们有像SIGUSR1 -> 12我们有类似的吗12 -> SIGUSR1 ?

Answer 1

我的strsignal(3)手册页说您可以直接从sys_signame数组中获得名称。下面是我编写的一个简单示例程序来测试它:

#include <signal.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
void upcase(char *s)
{
    while (*s)
    {
        *s = toupper(*s);
        s++;        
    }
}
int main(void)
{    
    for (int sig = 1; sig < NSIG; sig++)
    {
        char *str = strdup(sys_signame[sig]);
        if (!str)
            return -1;
        upcase(str);
        printf("%2d -> SIG%sn", sig, str);
        free(str);
    }
    return 0;
}

我认为这个程序会产生你想要的输出:

$ ./example 
 1 -> SIGHUP
 2 -> SIGINT
 3 -> SIGQUIT
 4 -> SIGILL
 5 -> SIGTRAP
 6 -> SIGABRT
 7 -> SIGEMT
 8 -> SIGFPE
 9 -> SIGKILL
10 -> SIGBUS
11 -> SIGSEGV
12 -> SIGSYS
13 -> SIGPIPE
14 -> SIGALRM
15 -> SIGTERM
16 -> SIGURG
17 -> SIGSTOP
18 -> SIGTSTP
19 -> SIGCONT
20 -> SIGCHLD
21 -> SIGTTIN
22 -> SIGTTOU
23 -> SIGIO
24 -> SIGXCPU
25 -> SIGXFSZ
26 -> SIGVTALRM
27 -> SIGPROF
28 -> SIGWINCH
29 -> SIGINFO
30 -> SIGUSR1
31 -> SIGUSR2

Answer 2

glib 2.32(发布于2020-08-05)引入了sigabbrev_np(int)函数。因为那个版本你不能再使用sys_siglist[]了。

From man strsignal:

sigabbrev_np()函数返回信号的缩写名sig。例如，给定值SIGINT，它返回字符串"INT"。
[…]
Sigdescr_np()和sigdabbrev_np()首次出现在glibc 2.32中。从2.32版本开始，sys_siglist符号不再被glibc导出。

从发行说明中:

新增sigabbrev_np、sigdescr_np功能。sigabbrev_np返回缩写信号名称(例如SIGHUP的"HUP")[…]对于无效的信号号，两个函数都返回NULL。

它们应该用来代替sys_siglist或sys_sigabbrev，它们都是线程和异步信号安全的。这些函数是GNU的扩展。

Answer 3

正如Jens Gustedt多年前在评论中指出的那样，sys_signame和sys_siglist是不可移植的。

由于这个问题被标记为[unix]，因此您可以以自己的方式移植#ifdef到特定于您的环境的名称和数值的映射。比如:

//
//  const char * signame(int s)
//
//    return the name of the given signal number as a string,
//    or NULL if the number is unrecognized.
//
#define _POSIX_C_SOURCE 200809L
#include <signal.h>
#define SIGNAMEANDNUM(s)  { #s, s }
static struct {
  const char *name,
  int value,
} known_signals[] = {
  SIGNAMEANDNUM(SIGABRT),   // get the POSIX signals
  SIGNAMEANDNUM(SIGALRM),
  SIGNAMEANDNUM(SIGBUS),
  SIGNAMEANDNUM(SIGCHLD),
  /* ... */
  SIGNAMEANDNUM(SIGXFSZ),
#ifdef SIGUNUSUAL           // get nonstandard signals 
  SIGNAMEANDNUM(SIGUNUSUAL),
#endif
  /* ... */
};
const char *
signame(int s) {
  const char *name = NULL;
  for (int i = 0; i < sizeof(known_signals)/sizeof(*known_signals); i++) {
    if (s == known_signals[i].value) {
      name = known_signals[i].name;
      break;
    }
  }
  return name;
}

当然，这需要对你的平台有一些先验的知识。

Answer 4

在Ubuntu 16.04和MIPS上测试了下面的代码，运行正常。

#include <signal.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
extern const char * const sys_siglist[];
void upcase(char *s)
{
    while (*s)
    {
        *s = toupper(*s);
        s++;
    }
}
int main(void)
{
    int sig;
    /*
       NSIG returns number of signals available in a system
       and it may vary according to platforms;Found on Ubuntu-16.04 it return 65
       where as in MIPS it is 31; Found in both the platforms it leads to core dump
       after signal 31 so limiting scanning of signal till 31 instead of using NSIG
    */
    for (sig = 1; sig < 32; sig++)
    {
        char *str = strdup(sys_siglist[sig]);
        if (!str)
            return -1;
        upcase(str);
        printf("%2d -> SIG%sn", sig, str);
        free(str);
    }
    return 0;
}

以上代码在Ubuntu-16.04 (Intel x86_64 GNU/Linux)上的输出:

 1 -> SIGHANGUP
 2 -> SIGINTERRUPT
 3 -> SIGQUIT
 4 -> SIGILLEGAL INSTRUCTION
 5 -> SIGTRACE/BREAKPOINT TRAP
 6 -> SIGABORTED
 7 -> SIGBUS ERROR
 8 -> SIGFLOATING POINT EXCEPTION
 9 -> SIGKILLED
10 -> SIGUSER DEFINED SIGNAL 1
11 -> SIGSEGMENTATION FAULT
12 -> SIGUSER DEFINED SIGNAL 2
13 -> SIGBROKEN PIPE
14 -> SIGALARM CLOCK
15 -> SIGTERMINATED
16 -> SIGSTACK FAULT
17 -> SIGCHILD EXITED
18 -> SIGCONTINUED
19 -> SIGSTOPPED (SIGNAL)
20 -> SIGSTOPPED
21 -> SIGSTOPPED (TTY INPUT)
22 -> SIGSTOPPED (TTY OUTPUT)
23 -> SIGURGENT I/O CONDITION
24 -> SIGCPU TIME LIMIT EXCEEDED
25 -> SIGFILE SIZE LIMIT EXCEEDED
26 -> SIGVIRTUAL TIMER EXPIRED
27 -> SIGPROFILING TIMER EXPIRED
28 -> SIGWINDOW CHANGED
29 -> SIGI/O POSSIBLE
30 -> SIGPOWER FAILURE
31 -> SIGBAD SYSTEM CALL

上述代码在busybox (MIPS, Cavium)上的输出:

 1 -> SIGHANGUP
 2 -> SIGINTERRUPT
 3 -> SIGQUIT
 4 -> SIGILLEGAL INSTRUCTION
 5 -> SIGTRACE/BREAKPOINT TRAP
 6 -> SIGABORTED
 7 -> SIGEMT TRAP
 8 -> SIGFLOATING POINT EXCEPTION
 9 -> SIGKILLED
10 -> SIGBUS ERROR
11 -> SIGSEGMENTATION FAULT
12 -> SIGBAD SYSTEM CALL
13 -> SIGBROKEN PIPE
14 -> SIGALARM CLOCK
15 -> SIGTERMINATED
16 -> SIGUSER DEFINED SIGNAL 1
17 -> SIGUSER DEFINED SIGNAL 2
18 -> SIGCHILD EXITED
19 -> SIGPOWER FAILURE
20 -> SIGWINDOW CHANGED
21 -> SIGURGENT I/O CONDITION
22 -> SIGI/O POSSIBLE
23 -> SIGSTOPPED (SIGNAL)
24 -> SIGSTOPPED
25 -> SIGCONTINUED
26 -> SIGSTOPPED (TTY INPUT)
27 -> SIGSTOPPED (TTY OUTPUT)
28 -> SIGVIRTUAL TIMER EXPIRED
29 -> SIGPROFILING TIMER EXPIRED
30 -> SIGCPU TIME LIMIT EXCEEDED
31 -> SIGFILE SIZE LIMIT EXCEEDED

Answer 5

可以，您可以声明一个全局数组，像这样

char *signame[]={"INVALID", "SIGHUP", "SIGINT", "SIGQUIT", "SIGILL", "SIGTRAP", "SIGABRT", "SIGBUS", "SIGFPE", "SIGKILL", "SIGUSR1", "SIGSEGV", "SIGUSR2", "SIGPIPE", "SIGALRM", "SIGTERM", "SIGSTKFLT", "SIGCHLD", "SIGCONT", "SIGSTOP", "SIGTSTP", "SIGTTIN", "SIGTTOU", "SIGURG", "SIGXCPU", "SIGXFSZ", "SIGVTALRM", "SIGPROF", "SIGWINCH", "SIGPOLL", "SIGPWR", "SIGSYS", NULL};

，并可以使用它在信号处理程序中打印信号名称，如

void sig_handler(int signum){
     printf("Received signal : %sn", signame[signum]);
}