implement process enumeration by executable name

include/debug.h

@@ -0,0 +1,11 @@
+#ifndef __DEBUG_H
+#define __DEBUG_H
+
+#ifdef DEBUG
+#include <stdio.h>
+#define TRACE(fmt, ...) fprintf(stderr, "%s:%d:%s\tTRACE\t" fmt, __FILE__, __LINE__, __func__, ##__VA_ARGS__)
+#else
+#define TRACE(fmt, ...)
+#endif
+
+#endif

include/process.h

@@ -28,6 +28,13 @@ typedef struct {
     gid_t gid;
 } process_status_t;
 
+// parse process status from procfs. returns 0 no errors and 1 on any kind of error
+// error information obtain from errno
 int process_parse_status(pid_t pid, process_status_t* status);
 
+// find any process that matches name, case insensitive.
+// list pointer must point to NULL-initialized pointer, and count pointer must pount to initialized 0
+// will skip any process which status couldn't be parsed 
+int processes_by_name(const char* name, process_status_t** list, size_t* count);
+
 #endif

src/main.c

@@ -1,21 +1,32 @@
 #include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include "process.h"
 
+void print_process(process_status_t* proc)
+{
+    puts("Process:");
+    printf("name: %s\n", proc->name);
+    printf("umask: %d\n", proc->umask);
+    printf("state: %d\n", proc->state);
+    printf("tgid: %d\n", proc->tgid);
+    printf("ngid: %d\n", proc->ngid);
+    printf("pid: %d\n", proc->pid);
+    printf("ppid: %d\n", proc->ppid);
+    printf("tracer_pid: %d\n", proc->tracer_pid);
+    printf("uid: %d\n", proc->uid);
+    printf("gid: %d\n", proc->gid);
+}
+
 int main(int argc, char** argv)
 {
-    process_status_t status = {};
+    process_status_t* list = NULL;
-    process_parse_status(getpid(), &status);
+    size_t count = 0;
 
-    printf("name: %s\n", status.name);
+    processes_by_name("dummy_target", &list, &count);
-    printf("umask: %d\n", status.umask);
+    for (size_t i = 0; i < count; i++)
-    printf("state: %d\n", status.state);
+        print_process(&list[i]);
-    printf("tgid: %d\n", status.tgid);
-    printf("ngid: %d\n", status.ngid);
-    printf("pid: %d\n", status.pid);
-    printf("ppid: %d\n", status.ppid);
-    printf("tracer_pid: %d\n", status.tracer_pid);
-    printf("uid: %d\n", status.uid);
-    printf("gid: %d\n", status.gid);
     
+    free(list);
     return 0;
 }

src/process.c

@@ -1,9 +1,13 @@
+#define _DEFAULT_SOURCE
 #include "process.h"
+#include "debug.h"
 #include <unistd.h>
 #include <fcntl.h>
+#include <dirent.h>
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <ctype.h>
 
 int process_parse_status(pid_t pid, process_status_t* status)
 {
@@ -52,3 +56,59 @@ int process_parse_status(pid_t pid, process_status_t* status)
 
     return 0;
 }
+
+static int is_numeric(const char* str)
+{
+    for (const char* p = str; *p; p++)
+        if (!isdigit(*p)) return 0;
+
+    return 1;
+}
+
+int processes_by_name(const char* name, process_status_t** list, size_t* count)
+{
+    DIR* proc = opendir("/proc");
+    if (!proc) return 1;
+
+    struct dirent* entry;
+    while ((entry = readdir(proc)))
+    {
+        if (entry->d_type != DT_DIR) continue;
+        if (!is_numeric(entry->d_name)) continue;
+
+        pid_t pid = strtod(entry->d_name, NULL);
+        process_status_t status = {};
+        if (process_parse_status(pid, &status))
+        {
+            TRACE("process parse status failed for %d\n", pid);
+            continue;
+        }
+
+        if (!strcasecmp(status.name, name))
+        {
+            // we have match! lets add it to list
+            size_t _count = *count;
+            process_status_t* _list = *list;
+            
+            if (_count) _list = (process_status_t*)realloc(_list, ++_count * sizeof(process_status_t));
+            else _list = (process_status_t*)malloc(++_count * sizeof(process_status_t));
+
+            if (!_list)
+            {
+                TRACE("out of memory for process status!\n");
+                closedir(proc);
+                return 1;
+            }
+
+            // copy process status to list
+            memcpy(&_list[_count - 1], &status, sizeof(process_status_t));
+
+            // update pointers
+            *list = _list;
+            *count = _count;
+        }
+    }
+
+    closedir(proc);
+    return 0;
+}