Initial commit of first working version

This supports the -c,--cmdline option as well as extended regexes
(hardcoded to case sensitive at this time). A help text is included with
a README and this is licensed under the GPLv3 license.

1 files changed, 130 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..2891623
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,130 @@
+/**
+ * Process snapshot utility with regex support
+ * Copyright (C) 2022  Aaron Ball <nullspoon@oper.io>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <regex.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <dirent.h>
+
+struct config {
+  int print_cmdline;
+  const char* regex;
+};
+
+int re_match(char* str, char* restr) {
+  regex_t regex;
+  regmatch_t pmatch[1];
+
+  if(regcomp(&regex, restr, REG_EXTENDED) != 0) {
+    puts("Error compiling regex");
+    puts(strerror(errno));
+    return -1;
+  }
+  return regexec(&regex, str, 1, pmatch, 0);
+}
+
+int read_cmdline(char* path, char* out, int size) {
+  FILE* fd = NULL;
+  int i = 0;
+  fd = fopen(path, "r");
+  while((out[i] = fgetc(fd)) != EOF) {
+    // Stop reading at double null byte
+    if(out[i] == 0 && out[i - 1] == 0)
+      break;
+    // Convert null bytes to spaces
+    if(out[i] == 0)
+      out[i] = ' ';
+    i++;
+  }
+  // Terminate string
+  out[i] = 0;
+  fclose(fd);
+  return 0;
+}
+
+int pid_search(struct config* c) {
+  DIR* dfd = NULL;
+  struct dirent* ent;
+  long pid = -1;
+  char pathbuf[64] = {'\0'};
+  char cmdbuf[512] = {'\0'};
+
+  dfd = opendir("/proc");
+
+  while((ent = readdir(dfd)) != NULL) {
+    if(ent->d_type != DT_DIR)
+      continue;
+
+    pid = strtol(ent->d_name, NULL, 10);
+    if(pid == 0)
+      continue;
+
+    sprintf(pathbuf, "/proc/%ld/cmdline", pid);
+    read_cmdline(pathbuf, cmdbuf, 512);
+
+    if(re_match(cmdbuf, (char*) c->regex) == 0) {
+      fputs(ent->d_name, stdout);
+      if(c->print_cmdline) {
+        fputc('\t', stdout);
+        fputs(cmdbuf, stdout);
+      }
+      fputc('\n', stdout);
+    }
+  }
+
+  closedir(dfd);
+  return 0;
+}
+
+void gethelp() {
+  puts("psre - Process snapshot regex\n\n"
+  "Usage:\n"
+  "  psre [options] regex\n\n"
+  "Options:\n"
+  "  -c,--cmdline   Print cmdline with each matching pid\n"
+  "  -h,--help      Print this helptext\n"
+  );
+}
+
+int parseargs(struct config* c, int argc, char* argv[]) {
+  int i = 1;
+  c->print_cmdline = 0;
+  c->regex = ".*";
+
+  while(i < argc) {
+    if(strcmp(argv[i], "-c") == 0 || strcmp(argv[i], "--cmdline") == 0) {
+      c->print_cmdline = 1;
+    } else if(strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
+      gethelp();
+      return -1;
+    } else {
+      c->regex = argv[i];
+    }
+
+    i++;
+  }
+  return 0;
+}
+
+int main(int argc, char* argv[]) {
+  struct config c;
+  if(parseargs(&c, argc, argv) != 0)
+    return 1;
+
+  pid_search(&c);
+  return 0;
+}