Question

标题可能听起来有点奇怪，ps aux我看到了：

root     20953  0.0  0.0   9528  1280 ?        Ss   Apr28   0:07 sendmail: accepting connections

其中“接受连接”就像是sendmail进程的标题。它不是一个参数，因为cat /proc/20953/cmdline返回sendmail: accepting connections（空格而不是0x00）：

# cat /proc/20953/cmdline |hexdump -C
00000000  73 65 6e 64 6d 61 69 6c  3a 20 61 63 63 65 70 74  |sendmail: accept|
00000010  69 6e 67 20 63 6f 6e 6e  65 63 74 69 6f 6e 73     |ing connections|
0000001f

/ proc fs中的参数用空字节分隔：

# cat /proc/26511/cmdline |hexdump -C
00000000  2f 62 69 6e 2f 62 61 73  68 00 2f 77 65 62 72 6f  |/bin/bash./webro|
00000010  6f 74 2f 70 72 6f 72 61  69 6c 2f 73 63 72 69 70  |ot/prorail/scrip|
00000020  74 73 2f 73 79 6e 63 6c  6f 6f 70 2e 73 68 00     |ts/syncloop.sh.|
0000002f

因此，当我在C中执行fork（）时，如何设置此进程信息，以便我可以识别哪个进程是什么？

Answer 1

sendmail有多种方式，具体取决于系统中的sendmail / conf.c中的system.see setproctitle：

#define SPT_NONE        0       /* don't use it at all */
#define SPT_REUSEARGV   1       /* cover argv with title information */
#define SPT_BUILTIN     2       /* use libc builtin */
#define SPT_PSTAT       3       /* use pstat(PSTAT_SETCMD, ...) */
#define SPT_PSSTRINGS   4       /* use PS_STRINGS->... */
#define SPT_SYSMIPS     5       /* use sysmips() supported by NEWS-OS 6 */
#define SPT_SCO         6       /* write kernel u. area */
#define SPT_CHANGEARGV  7       /* write our own strings into argv[] */

有关详细信息，请参阅conf.c中的setproctitle例程。

Answer 2

我找到答案here虽然问题不是同一个问题。所有积分都应转到Chris Jester-Young

#include <string.h>
#include <unistd.h>

int main(int argc, char** argv)
{
    strcpy(argv[0], "Hello, world!");
    sleep(10);
    return 0;
}

Answer 3

在本文中：setproctitle() in Linux作者解释了如何更改流程标题。我猜setproctitle是available in BSD，所以他试图为linux实现它。以下是the function

的lxc library

我还没有测试过。我还没有检查它是否使用了库中的其他函数，因此代码可能不完整。随意测试并留下冥想。

/*
 * Sets the process title to the specified title. Note that this may fail if
 * the kernel doesn't support PR_SET_MM_MAP (kernels <3.18).
 */
int setproctitle(char *title)
{
    static char *proctitle = NULL;
    char buf[2048], *tmp;
    FILE *f;
    int i, len, ret = 0;

    /* We don't really need to know all of this stuff, but unfortunately
     * PR_SET_MM_MAP requires us to set it all at once, so we have to
     * figure it out anyway.
     */
    unsigned long start_data, end_data, start_brk, start_code, end_code,
            start_stack, arg_start, arg_end, env_start, env_end,
            brk_val;
    struct prctl_mm_map prctl_map;

    f = fopen_cloexec("/proc/self/stat", "r");
    if (!f) {
        return -1;
    }

    tmp = fgets(buf, sizeof(buf), f);
    fclose(f);
    if (!tmp) {
        return -1;
    }

    /* Skip the first 25 fields, column 26-28 are start_code, end_code,
     * and start_stack */
    tmp = strchr(buf, ' ');
    for (i = 0; i < 24; i++) {
        if (!tmp)
            return -1;
        tmp = strchr(tmp+1, ' ');
    }
    if (!tmp)
        return -1;

    i = sscanf(tmp, "%lu %lu %lu", &start_code, &end_code, &start_stack);
    if (i != 3)
        return -1;

    /* Skip the next 19 fields, column 45-51 are start_data to arg_end */
    for (i = 0; i < 19; i++) {
        if (!tmp)
            return -1;
        tmp = strchr(tmp+1, ' ');
    }

    if (!tmp)
        return -1;

    i = sscanf(tmp, "%lu %lu %lu %*u %*u %lu %lu",
        &start_data,
        &end_data,
        &start_brk,
        &env_start,
        &env_end);
    if (i != 5)
        return -1;

    /* Include the null byte here, because in the calculations below we
     * want to have room for it. */
    len = strlen(title) + 1;

    proctitle = realloc(proctitle, len);
    if (!proctitle)
        return -1;

    arg_start = (unsigned long) proctitle;
    arg_end = arg_start + len;

    brk_val = syscall(__NR_brk, 0);

    prctl_map = (struct prctl_mm_map) {
        .start_code = start_code,
        .end_code = end_code,
        .start_stack = start_stack,
        .start_data = start_data,
        .end_data = end_data,
        .start_brk = start_brk,
        .brk = brk_val,
        .arg_start = arg_start,
        .arg_end = arg_end,
        .env_start = env_start,
        .env_end = env_end,
        .auxv = NULL,
        .auxv_size = 0,
        .exe_fd = -1,
    };

    ret = prctl(PR_SET_MM, PR_SET_MM_MAP, (long) &prctl_map, sizeof(prctl_map), 0);
    if (ret == 0)
        strcpy((char*)arg_start, title);
    else
        INFO("setting cmdline failed - %s", strerror(errno));

    return ret;
}

Linux - 如何在C中更改分叉进程的信息

3 个答案: