First version of the export command

1 files changed, 105 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
index 15b658c..2a666db 100644
--- a/src/main.c
+++ b/src/main.c
@@ -8,6 +8,7 @@
 #include <string.h>
 #include <sys/sendfile.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <time.h>
 #include <unistd.h>
 
@@ -199,6 +200,109 @@ static int table_next_id(sqlite3 *db, const char *table)
 	return last_id + 1;
 }
 
+static void ftag_export_help(void)
+{
+	printf("Usage: ftag export [OPTION]... ARCHIVE\n");
+	printf("Export files from the database to an archive. Files are read from\n");
+	printf("standard input, one per line. Files have to be canonical names that\n");
+	printf("exist in the database.\n");
+	/* TODO: support files outside of the database
+
+	   A file name starting with a slash can be considered as a file to take
+	   from the filesystem, not from the database. */
+	printf("Available options:\n");
+	printf("  -h  print this help\n");
+	printf("  -n  TODO: add user name as a suffix\n");
+	printf("  -f  TODO: use files' full names\n");
+}
+
+static void ftag_export(int argc, char **argv)
+{
+	if (argc != 1) {
+		ftag_export_help();
+		exit(EXIT_FAILURE);
+	}
+	char *archive_dir = argv[0];
+
+	char archive_file[64];
+	strcpy(archive_file, archive_dir);
+	strcat(archive_file, ".tar.gz");
+
+	/* step 1: create temporary directory having the name of the archive */
+	char tmp_dir[64];
+	strcpy(tmp_dir, "/tmp/");
+	strcat(tmp_dir, archive_dir);
+	int rc = mkdir(tmp_dir, 0755);
+	if (rc == -1) {
+		fprintf(stderr, "mkdir: %s:", tmp_dir);
+		perror("");
+		exit(EXIT_FAILURE);
+	}
+
+	/* step 2: copy archive files to the temporary directory */
+	size_t line_size = 256;
+	ssize_t line_len;
+	char *line = malloc(line_size);
+	char in[512];
+	int in_fd;
+	char out[128];
+	int out_fd;
+	while ((line_len = getline(&line, &line_size, stdin)) != -1) {
+		remove_ending_newline(line);
+		snprintf(in, sizeof(in)-1, "%s/files/%s", FTAG_ROOT, line);
+		snprintf(out, sizeof(out)-1, "%s/%s", tmp_dir, line);
+		in_fd = open(in, O_RDONLY);
+		if (in_fd == -1) {
+			fprintf(stderr, "open: %s:", in);
+			perror("");
+			exit(EXIT_FAILURE);
+		}
+		out_fd = open(out, O_WRONLY | O_CREAT, 0644);
+		if (out_fd == -1) {
+			fprintf(stderr, "open: %s:", out);
+			perror("");
+			exit(EXIT_FAILURE);
+		}
+		ssize_t written_bytes;
+		while ((written_bytes = sendfile(out_fd, in_fd, NULL, 4096)) == 4096)
+			;
+		close(in_fd);
+		close(out_fd);
+	}
+	free(line);
+
+	/* step 3: invoke tar to build the archive */
+	rc = fork();
+	if (rc == 0) {
+		execlp("tar",
+		       "tar",
+		       "--directory", "/tmp",
+		       "--create",
+		       "--gzip",
+		       "--file", archive_file,
+		       archive_dir,
+		       NULL);
+		fprintf(stderr, "exec: tar:");
+		perror("");
+		exit(EXIT_FAILURE);
+	}
+	else if (rc > 0) {
+		int status;
+		wait(&status);
+		if (!(WIFEXITED(status) && WEXITSTATUS(status) == 0)) {
+			fprintf(stderr, "ftag export: child process exited abnormally\n");
+			exit(EXIT_FAILURE);
+		}
+	}
+	else {
+		perror("fork");
+		exit(EXIT_FAILURE);
+	}
+
+	/* step 4: clean /tmp */
+	execlp("rm", "rm", "--recursive", "--force", tmp_dir, NULL);
+}
+
 /* Create ftag's database and directories. */
 static void ftag_init(int, char **)
 {
@@ -869,6 +973,7 @@ int main(int argc, char *argv[])
 	}
 
 	const struct ftag_command toplevel_commands[] = {
+		{.name = "export", .func = ftag_export},
 		{.name = "init",   .func = ftag_init},
 		{.name = "file",   .func = ftag_file},
 		{.name = "-h",     .func = ftag_help},