misc/find_program.h: Look in PATH first.

misc/find_program.h

@@ -37,9 +37,11 @@
 
 #include <stdlib.h>
 #include <unistd.h>
+#include <string.h>
 
 #include <misc/concat_strings.h>
 #include <misc/debug.h>
+#include <misc/balloc.h>
 
 static char * badvpn_find_program (const char *name);
 
@@ -47,6 +49,38 @@ static char * badvpn_find_program (const char *name)
 {
     ASSERT(name)
     
+    char *path = getenv("PATH");
+    if (path) {
+        while (1) {
+            size_t i = 0;
+            while (path[i] != ':' && path[i] != '\0') {
+                i++;
+            }
+            char const *src = path;
+            size_t src_len = i;
+            if (src_len == 0) {
+                src = ".";
+                src_len = 1;
+            }
+            size_t name_len = strlen(name);
+            char *entry = BAllocSize(bsize_add(bsize_fromsize(src_len), bsize_add(bsize_fromsize(name_len), bsize_fromsize(2))));
+            if (!entry) {
+                goto fail;
+            }
+            memcpy(entry, src, src_len);
+            entry[src_len] = '/';
+            strcpy(entry + (src_len + 1), name);
+            if (access(entry, X_OK) == 0) {
+                return entry;
+            }
+            free(entry);
+            if (path[i] == '\0') {
+                break;
+            }
+            path += i + 1;
+        }
+    }
+    
     const char *dirs[] = {"/usr/sbin", "/usr/bin", "/sbin", "/bin", NULL};
     
     for (size_t i = 0; dirs[i]; i++) {