file: Truncate file before rewriting it

It can happen that the file is shorter after we have fixed the
interpreter, which causes that the remaining data is still in the file.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

diff --git a/src/libpakfire/file.c b/src/libpakfire/file.c
index 7a994c48fc4b16f86a31e2b31f26569b4a96d8ea..5655b4b7190cb16c6baf92472f387bd6724c44fc 100644 (file)
--- a/src/libpakfire/file.c
+++ b/src/libpakfire/file.c
@@ -2421,6 +2421,7 @@ static int pakfire_file_fix_interpreter(struct pakfire_file* file, const char* i
        int r;
 
        char* buffer = NULL;
+       size_t l = 0;
        char* line = NULL;
        size_t length = 0;
        char* p = NULL;
@@ -2526,6 +2527,9 @@ static int pakfire_file_fix_interpreter(struct pakfire_file* file, const char* i
                                if (r < 0)
                                        goto ERROR;
 
+                               // Store length of the buffer
+                               l = r;
+
                                // Process the next line
                                break;
 
@@ -2534,6 +2538,10 @@ static int pakfire_file_fix_interpreter(struct pakfire_file* file, const char* i
                                r = asprintf(&buffer, "%s%s", buffer, line);
                                if (r < 0)
                                        goto ERROR;
+
+                               // Store length of the buffer
+                               l = r;
+
                                break;
                }
        }
@@ -2541,10 +2549,18 @@ static int pakfire_file_fix_interpreter(struct pakfire_file* file, const char* i
        // Go back to the beginning of the file
        rewind(f);
 
+       // Truncate the existing content
+       r = ftruncate(fileno(f), 0);
+       if (r) {
+               ERROR(file->pakfire, "Could not truncate %s: %m\n", path);
+               r = -errno;
+               goto ERROR;
+       }
+
        // Write back the buffer
        if (buffer) {
-               size_t bytes_written = fwrite(buffer, 1, strlen(buffer), f);
-               if (bytes_written < length) {
+               size_t bytes_written = fwrite(buffer, 1, l, f);
+               if (bytes_written < l) {
                        ERROR(file->pakfire, "%s: Could not write the payload: %m\n", path);
                        r = -errno;
                        goto ERROR;