Enrico Fraccaroli
130 lines
3.9 KiB
C
130 lines
3.9 KiB
C
/// MentOS, The Mentoring Operating system project
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/// @file ps.c
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/// @brief Report a snapshot of the current processes.
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/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#include <sys/unistd.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <strerror.h>
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#include <string.h>
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#define FORMAT_S "%5s %5s %6s %s\n"
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#define FORMAT "%5d %5d %6c %s\n"
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static inline void __iterate_proc_dirs(int fd)
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{
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char absolute_path[PATH_MAX] = "/proc/";
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// Holds the file descriptor of the stat file.
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int stat_fd;
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// Buffer used to read the stat file.
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char stat_buffer[BUFSIZ] = { 0 };
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// Holds the number of bytes read from stat file.
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ssize_t ret;
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// Variables used to read the stat file.
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// (1) pid %d
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// (2) comm %s
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// (3) state %c
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// (4) ppid %d
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pid_t pid;
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char comm[BUFSIZ] = { 0 };
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char state;
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pid_t ppid;
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// The directory entry.
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dirent_t dent;
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while (getdents(fd, &dent, sizeof(dirent_t)) == sizeof(dirent_t)) {
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// Skip non-directories.
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if (dent.d_type != DT_DIR)
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continue;
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// Build the path to the stat file (i.e., `/proc/<pid>/stat`).
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strcpy(absolute_path + 6, dent.d_name);
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strcat(absolute_path, "/stat");
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// Open the `/proc/<pid>/stat` file.
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if ((stat_fd = open(absolute_path, O_RDONLY, 0)) == -1) {
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printf("Failed to open `%s`\n", absolute_path);
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continue;
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}
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// Reset the stat buffer.
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memset(stat_buffer, 0, BUFSIZ);
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// Read the content of the stat file.
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if ((ret = read(stat_fd, stat_buffer, BUFSIZ)) <= 0) {
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printf("Cannot read `%s`\n", absolute_path);
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close(stat_fd);
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continue;
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}
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// Reset the comm buffer.
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memset(comm, 0, BUFSIZ);
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// Parse the content of the stat file.
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sscanf(stat_buffer, "%d %s %c %d", &pid, comm, &state, &ppid);
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// Print the stats concerning the process.
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printf(FORMAT, pid, ppid, state, comm);
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// Closing stat FD.
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close(stat_fd);
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}
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}
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int main(int argc, char **argv)
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{
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int fd = open("/proc", O_RDONLY | O_DIRECTORY, 0);
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if (fd == -1) {
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printf("ps: cannot access '/proc': %s\n\n", strerror(errno));
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} else {
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printf(FORMAT_S, "PID", "PPID", "STATUS", "CMD");
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__iterate_proc_dirs(fd);
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close(fd);
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}
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#if 0
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DIR *dir;
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struct dirent_t *ent;
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int i, fd_self, fd;
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unsigned long time, stime;
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char flag, *tty;
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char cmd[256], tty_self[256], path[256], time_s[256];
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FILE *file;
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dir = opendir("/proc");
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fd_self = open("/proc/self/fd/0", O_RDONLY);
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sprintf(tty_self, "%s", ttyname(fd_self));
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printf(FORMAT, "PID", "TTY", "TIME", "CMD");
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while ((ent = readdir(dir)) != NULL) {
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flag = 1;
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for (i = 0; ent->d_name[i]; i++)
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if (!isdigit(ent->d_name[i])) {
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flag = 0;
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break;
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}
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if (flag) {
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sprintf(path, "/proc/%s/fd/0", ent->d_name);
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fd = open(path, O_RDONLY);
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tty = ttyname(fd);
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if (tty && strcmp(tty, tty_self) == 0) {
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sprintf(path, "/proc/%s/stat", ent->d_name);
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file = fopen(path, "r");
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fscanf(file, "%d%s%c%c%c", &i, cmd, &flag, &flag, &flag);
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cmd[strlen(cmd) - 1] = '\0';
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for (i = 0; i < 11; i++)
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fscanf(file, "%lu", &time);
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fscanf(file, "%lu", &stime);
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time = (int)((double)(time + stime) / sysconf(_SC_CLK_TCK));
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sprintf(time_s, "%02lu:%02lu:%02lu",
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(time / 3600) % 3600, (time / 60) % 60, time % 60);
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printf(FORMAT, ent->d_name, tty + 5, time_s, cmd + 1);
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fclose(file);
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}
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close(fd);
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}
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}
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close(fd_self);
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#endif
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return 0;
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}
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