Enrico Fraccaroli (Galfurian)
96 lines
2.8 KiB
C
96 lines
2.8 KiB
C
/// @file ps.c
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/// @brief Report a snapshot of the current processes.
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/// @copyright (c) 2014-2024 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 <string.h>
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#include <stdlib.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 proc_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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// 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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// Holds the number of bytes read.
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ssize_t read_bytes;
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do {
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// Read an entry.
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read_bytes = getdents(proc_fd, &dent, sizeof(dirent_t));
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// We reached the end of the folder.
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if (read_bytes == 0) {
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break;
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}
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// We encountered an error.
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if (read_bytes == -1) {
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perror("Failed to read entry in `/proc` folder");
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exit(EXIT_FAILURE);
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}
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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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}
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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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stat_fd = open(absolute_path, O_RDONLY, 0);
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if (stat_fd == -1) {
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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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read_bytes = read(stat_fd, stat_buffer, BUFSIZ);
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// Check if the read failed.
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if (read_bytes <= 0) {
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printf("Cannot read `%s`", absolute_path);
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perror(NULL);
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putchar('\n');
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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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} while (1);
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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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perror("ps: cannot access '/proc' folder");
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return EXIT_FAILURE;
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}
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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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putchar('\n');
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return EXIT_SUCCESS;
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}
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