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authorLennart Poettering <lennart@poettering.net>2015-11-13 00:54:56 +0100
committerLennart Poettering <lennart@poettering.net>2015-11-13 13:02:49 +0100
commiteb3da9012f462da2451edeb8d67c5b67c833a0b1 (patch)
treec009896e29778ebe5ac2fdcb140f5fdb27aa2788 /src/basic
parent87fde73e185fabc346ee4d9c9befe972e3502dc3 (diff)
util-lib: optionally, when writing a string to a file, verify string on failure
With this change, the idiom: r = write_string_file(p, buf, 0); if (r < 0) { if (verify_one_line_file(p, buf) > 0) r = 0; } gets reduced to: r = write_string_file(p, buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE); i.e. when writing the string fails and the new flag WRITE_STRING_FILE_VERIFY_ON_FAILURE is specified we'll not return a failure immediately, but check the contents of the file. If it matches what we wanted to write we suppress the error and exit cleanly.
Diffstat (limited to 'src/basic')
-rw-r--r--src/basic/fileio.c83
-rw-r--r--src/basic/fileio.h3
2 files changed, 71 insertions, 15 deletions
diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index be6e327690..10aacdc56d 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -78,6 +78,7 @@ static int write_string_file_atomic(const char *fn, const char *line, bool enfor
int write_string_file(const char *fn, const char *line, WriteStringFileFlags flags) {
_cleanup_fclose_ FILE *f = NULL;
+ int q, r;
assert(fn);
assert(line);
@@ -85,30 +86,58 @@ int write_string_file(const char *fn, const char *line, WriteStringFileFlags fla
if (flags & WRITE_STRING_FILE_ATOMIC) {
assert(flags & WRITE_STRING_FILE_CREATE);
- return write_string_file_atomic(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
+ r = write_string_file_atomic(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
+ if (r < 0)
+ goto fail;
+
+ return r;
}
if (flags & WRITE_STRING_FILE_CREATE) {
f = fopen(fn, "we");
- if (!f)
- return -errno;
+ if (!f) {
+ r = -errno;
+ goto fail;
+ }
} else {
int fd;
/* We manually build our own version of fopen(..., "we") that
* works without O_CREAT */
fd = open(fn, O_WRONLY|O_CLOEXEC|O_NOCTTY);
- if (fd < 0)
- return -errno;
+ if (fd < 0) {
+ r = -errno;
+ goto fail;
+ }
f = fdopen(fd, "we");
if (!f) {
+ r = -errno;
safe_close(fd);
- return -errno;
+ goto fail;
}
}
- return write_string_stream(f, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
+ r = write_string_stream(f, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
+ if (r < 0)
+ goto fail;
+
+ return 0;
+
+fail:
+ if (!(flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE))
+ return r;
+
+ f = safe_fclose(f);
+
+ /* OK, the operation failed, but let's see if the right
+ * contents in place already. If so, eat up the error. */
+
+ q = verify_file(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
+ if (q <= 0)
+ return r;
+
+ return 0;
}
int read_one_line_file(const char *fn, char **line) {
@@ -139,15 +168,41 @@ int read_one_line_file(const char *fn, char **line) {
return 0;
}
-int verify_one_line_file(const char *fn, const char *line) {
- _cleanup_free_ char *value = NULL;
- int r;
+int verify_file(const char *fn, const char *blob, bool accept_extra_nl) {
+ _cleanup_fclose_ FILE *f = NULL;
+ _cleanup_free_ char *buf = NULL;
+ size_t l, k;
- r = read_one_line_file(fn, &value);
- if (r < 0)
- return r;
+ assert(fn);
+ assert(blob);
+
+ l = strlen(blob);
+
+ if (accept_extra_nl && endswith(blob, "\n"))
+ accept_extra_nl = false;
+
+ buf = malloc(l + accept_extra_nl + 1);
+ if (!buf)
+ return -ENOMEM;
- return streq(value, line);
+ f = fopen(fn, "re");
+ if (!f)
+ return -errno;
+
+ /* We try to read one byte more than we need, so that we know whether we hit eof */
+ errno = 0;
+ k = fread(buf, 1, l + accept_extra_nl + 1, f);
+ if (ferror(f))
+ return errno > 0 ? -errno : -EIO;
+
+ if (k != l && k != l + accept_extra_nl)
+ return 0;
+ if (memcmp(buf, blob, l) != 0)
+ return 0;
+ if (k > l && buf[l] != '\n')
+ return 0;
+
+ return 1;
}
int read_full_stream(FILE *f, char **contents, size_t *size) {
diff --git a/src/basic/fileio.h b/src/basic/fileio.h
index 5f2c941498..95e8698941 100644
--- a/src/basic/fileio.h
+++ b/src/basic/fileio.h
@@ -34,6 +34,7 @@ typedef enum {
WRITE_STRING_FILE_CREATE = 1,
WRITE_STRING_FILE_ATOMIC = 2,
WRITE_STRING_FILE_AVOID_NEWLINE = 4,
+ WRITE_STRING_FILE_VERIFY_ON_FAILURE = 8,
} WriteStringFileFlags;
int write_string_stream(FILE *f, const char *line, bool enforce_newline);
@@ -43,7 +44,7 @@ int read_one_line_file(const char *fn, char **line);
int read_full_file(const char *fn, char **contents, size_t *size);
int read_full_stream(FILE *f, char **contents, size_t *size);
-int verify_one_line_file(const char *fn, const char *line);
+int verify_file(const char *fn, const char *blob, bool accept_extra_nl);
int parse_env_file(const char *fname, const char *separator, ...) _sentinel_;
int load_env_file(FILE *f, const char *fname, const char *separator, char ***l);