c_cpp 在给定pid的情况下计算打开文件描述符的实用程序

Posted 2021-05-14

#include <sys/types.h>
#include <dirent.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define procDir "/proc"
#define defaultDelay 60

// Build: /opt/gcc-6/bin/gcc -m64 -lumem -Wall -o countfds ./countfds.c

/*
 * count_fds: Count number of of entries, each of which represents
 * an open file descriptor in directory by name in `path`.
 */
static int count_fds(const char *path) {
    struct dirent *dirp;
    DIR *dp;
    int nfds = 0;

    if ((dp = opendir(path)) == NULL) {
        perror("failed to open fd dir for process");
        return -1;
    }

    do {
        if ((dirp = readdir(dp)) != NULL) {
            if ((strcmp(".", dirp->d_name) == 0) ||
                (strcmp("..", dirp->d_name) == 0)) {
                    continue;
                }
            nfds++;
        }
    } while (dirp != NULL);

return nfds;
}

static void lookup(long pid)
{
    DIR *dp;
    struct dirent *dirp;
    char p[256];
    int ct = 0;

    if ((dp = opendir(procDir)) == NULL) {
            perror("couldn't open '.'");
            return;
    }
    do {
        errno = 0;
        if ((dirp = readdir(dp)) != NULL) {
            if (strcmp(dirp->d_name, ".") == 0 ||
                strcmp(dirp->d_name, "..") == 0) {
                continue;
            }
                (void) sprintf(p, "%s/%s/fd", procDir, dirp->d_name);
                if (strtol(dirp->d_name, NULL, 10) != pid)
                        continue;
                ct = count_fds(p);
                if (ct < 0) {
                    (void) fprintf(stderr,
                        "PID(%ld): failed counting descriptors\n", pid);
                } else {
                    (void) printf("PID(%ld): %d open descriptors\n", pid, ct);

                }
                return;
            }
    } while (dirp != NULL);

    if (errno != 0)
        perror("error reading directory");
    else
        (void) printf("failed to find %ld\n", pid);
    (void) closedir(dp);
    return;
}

int main(int argc, char *argv[])
{
    long pid;
    int i = 1, pids_idx = 0;
    long repeat = 0;
    long delay = 0;

    // Use FD_COUNT_DELAY to control interval between lookups.
    if (getenv("FD_COUNT_DELAY")!=NULL) {
        delay = strtol(getenv("FD_COUNT_DELAY"), NULL, 10);
        delay = delay == 0 ? defaultDelay : delay;
    }

    if (argv[1][0] == '-' && argv[1][1] == 'c' ) {
        if (argv[1][2] == '\0') {
            repeat = atol(argv[2]);
            i+=2;
        } else {
            repeat = atol(&argv[1][2]);
            i++;
        }
    }
    pids_idx = i;
    while (repeat--) {
        for (; i < argc; i++) {
            pid = strtol(argv[i], NULL, 10);
            if (pid < 0 || pid == 0) { // pid must be non-negative and >0 number
                continue;
            }
            lookup(pid);
        }
        i = pids_idx;
        sleep(delay);
    }
    return (0);
}