[PATCH] tar --to-command

Ladislav Michl Ladislav.Michl at seznam.cz
Thu Jun 24 13:33:55 UTC 2010


On Thu, Jun 24, 2010 at 04:51:49AM +0200, Denys Vlasenko wrote:
> On Monday 21 June 2010 19:41, Ladislav Michl wrote:
 
> Here is how mdev.c does it:
> 
>	char *s = xasprintf("%s=%s", "MDEV", node_name);
>	char *s1 = xasprintf("%s=%s", "SUBSYSTEM", G.subsystem);
>	putenv(s);
>	putenv(s1);
>	if (system(command) == -1)
>		bb_perror_msg("can't run '%s'", command);
>	bb_unsetenv(s1);
>	free(s1);
>	bb_unsetenv(s);
>	free(s);

Thanks for a pointer. Since putenv may fail, I used xputenv which could be
eventually moved to libbb.

> sighandler_t is a glibc'ism, some other libcs do not have
> that typedef. Use explicit void (*f)(int) type.
> Give sig_pipe better name (saved_sigpipe?).

Fixed. FYI there is one more sighandler_t occurence in libbb/lineedit.c

> Move signal(SIGPIPE, SIG_IGN) / signal(SIGPIPE, sig_pipe)
> out of the loop.

Do you mean into tar.c itself?

Here is v4, signal out of the loop remains unaddressed.

From: Ladislav Michl <ladis at linux-mips.org>

Implement GNU tar --to-command option.

Signed-off-by: Ladislav Michl <ladis at linux-mips.org>
---
 archival/libunarchive/data_extract_to_command.c |  141 ++++++++++++++++++++++++
 archival/Config.src                             |    9 +
 archival/libunarchive/Kbuild.src                |    1
 archival/tar.c                                  |    9 +
 include/unarchive.h                             |    4
 5 files changed, 164 insertions(+)

diff --git a/archival/Config.src b/archival/Config.src
index 3dbd3ae..3cc88c4 100644
--- a/archival/Config.src
+++ b/archival/Config.src
@@ -280,6 +280,15 @@ config FEATURE_TAR_LONG_OPTIONS
 	help
 	  Enable use of long options, increases size by about 400 Bytes
 
+config FEATURE_TAR_TO_COMMAND
+	bool "Support for writing to an external program"
+	default y
+	depends on TAR && FEATURE_TAR_LONG_OPTIONS
+	help
+	  If you enable this option you'll be able to instruct tar to send 
+	  the contents of each extracted file to the standard input of an
+	  external program.
+
 config FEATURE_TAR_UNAME_GNAME
 	bool "Enable use of user and group names"
 	default y
diff --git a/archival/libunarchive/Kbuild.src b/archival/libunarchive/Kbuild.src
index 8185455..ef31b31 100644
--- a/archival/libunarchive/Kbuild.src
+++ b/archival/libunarchive/Kbuild.src
@@ -53,6 +53,7 @@ lib-$(CONFIG_FEATURE_SEAMLESS_BZ2)      += open_transformer.o decompress_bunzip2
 lib-$(CONFIG_FEATURE_SEAMLESS_LZMA)     += open_transformer.o decompress_unlzma.o get_header_tar_lzma.o
 lib-$(CONFIG_FEATURE_SEAMLESS_XZ)       += open_transformer.o decompress_unxz.o
 lib-$(CONFIG_FEATURE_COMPRESS_USAGE)    += decompress_bunzip2.o
+lib-$(CONFIG_FEATURE_TAR_TO_COMMAND)	+= data_extract_to_command.o
 
 ifneq ($(lib-y),)
 lib-y += $(COMMON_FILES)
diff --git a/archival/tar.c b/archival/tar.c
index 3a94012..f7b0fe9 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -749,6 +749,7 @@ enum {
 	IF_FEATURE_SEAMLESS_GZ(  OPTBIT_GZIP        ,)
 	IF_FEATURE_SEAMLESS_Z(   OPTBIT_COMPRESS    ,) // 16th bit
 	IF_FEATURE_TAR_NOPRESERVE_TIME(OPTBIT_NOPRESERVE_TIME,)
+	IF_FEATURE_TAR_TO_COMMAND(OPTBIT_2COMMAND,)
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS
 	OPTBIT_NUMERIC_OWNER,
 	OPTBIT_NOPRESERVE_PERM,
@@ -772,6 +773,7 @@ enum {
 	OPT_GZIP         = IF_FEATURE_SEAMLESS_GZ(  (1 << OPTBIT_GZIP        )) + 0, // z
 	OPT_COMPRESS     = IF_FEATURE_SEAMLESS_Z(   (1 << OPTBIT_COMPRESS    )) + 0, // Z
 	OPT_NOPRESERVE_TIME = IF_FEATURE_TAR_NOPRESERVE_TIME((1 << OPTBIT_NOPRESERVE_TIME)) + 0, // m
+	OPT_2COMMAND        = IF_FEATURE_TAR_TO_COMMAND(  (1 << OPTBIT_2COMMAND       )) + 0, // to-command
 	OPT_NUMERIC_OWNER   = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NUMERIC_OWNER  )) + 0, // numeric-owner
 	OPT_NOPRESERVE_PERM = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NOPRESERVE_PERM)) + 0, // no-same-permissions
 	OPT_OVERWRITE       = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_OVERWRITE      )) + 0, // overwrite
@@ -813,6 +815,9 @@ static const char tar_longopts[] ALIGN1 =
 # if ENABLE_FEATURE_TAR_NOPRESERVE_TIME
 	"touch\0"               No_argument       "m"
 # endif
+# if ENABLE_FEATURE_TAR_TO_COMMAND
+	"to-command\0"		Required_argument "\xfb"
+# endif
 	/* use numeric uid/gid from tar header, not textual */
 	"numeric-owner\0"       No_argument       "\xfc"
 	/* do not restore mode */
@@ -904,6 +909,7 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 		, &tar_filename // -f filename
 		IF_FEATURE_TAR_FROM(, &(tar_handle->accept)) // T
 		IF_FEATURE_TAR_FROM(, &(tar_handle->reject)) // X
+		IF_FEATURE_TAR_TO_COMMAND(, &(tar_handle->tar__to_command))
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS && ENABLE_FEATURE_TAR_FROM
 		, &excludes // --exclude
 #endif
@@ -922,6 +928,9 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 	if (opt & OPT_2STDOUT)
 		tar_handle->action_data = data_extract_to_stdout;
 
+	if (opt & OPT_2COMMAND)
+		tar_handle->action_data = data_extract_to_command;
+
 	if (opt & OPT_KEEP_OLD)
 		tar_handle->ah_flags &= ~ARCHIVE_UNLINK_OLD;
 
diff --git a/include/unarchive.h b/include/unarchive.h
index 8009de2..f3aa05d 100644
--- a/include/unarchive.h
+++ b/include/unarchive.h
@@ -75,6 +75,9 @@ typedef struct archive_handle_t {
 	char* tar__longname;
 	char* tar__linkname;
 # endif
+#if ENABLE_FEATURE_TAR_TO_COMMAND
+	char* tar__to_command;
+#endif
 # if ENABLE_FEATURE_TAR_SELINUX
 	char* tar__global_sctx;
 	char* tar__next_file_sctx;
@@ -128,6 +131,7 @@ extern void unpack_ar_archive(archive_handle_t *ar_archive) FAST_FUNC;
 extern void data_skip(archive_handle_t *archive_handle) FAST_FUNC;
 extern void data_extract_all(archive_handle_t *archive_handle) FAST_FUNC;
 extern void data_extract_to_stdout(archive_handle_t *archive_handle) FAST_FUNC;
+extern void data_extract_to_command(archive_handle_t *archive_handle) FAST_FUNC;
 
 extern void header_skip(const file_header_t *file_header) FAST_FUNC;
 extern void header_list(const file_header_t *file_header) FAST_FUNC;
--- a/archival/libunarchive/data_extract_to_command.c	2010-06-24 10:19:42.543380665 +0200
+++ b/archival/libunarchive/data_extract_to_command.c	2010-06-24 15:09:30.000000000 +0200
@@ -0,0 +1,141 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+#include "unarchive.h"
+
+enum {
+	TAR_FILETYPE,
+	TAR_MODE,
+	TAR_FILENAME,
+	TAR_REALNAME,
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+	TAR_UNAME,
+	TAR_GNAME,
+#endif
+	TAR_SIZE,
+	TAR_UID,
+	TAR_GID,
+	TAR_MAX,
+};
+
+static const char *const tar_var[] = {
+	"FILETYPE",
+	"MODE",
+	"FILENAME",
+	"REALNAME",
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+	"UNAME",
+	"GNAME",
+#endif
+	"SIZE",
+	"UID",
+	"GID",
+};
+
+static void xputenv(char *str)
+{
+	if (putenv(str))
+		bb_error_msg_and_die(bb_msg_memory_exhausted);
+}
+
+static void str2env(char *env[], int idx, const char *str)
+{
+	env[idx] = xasprintf("TAR_%s=%s", tar_var[idx], str);
+	xputenv(env[idx]);
+}
+
+static void dec2env(char *env[], int idx, unsigned long val)
+{
+	env[idx] = xasprintf("TAR_%s=%ld", tar_var[idx], val);
+	xputenv(env[idx]);
+}
+
+static void oct2env(char *env[], int idx, unsigned long val)
+{
+	env[idx] = xasprintf("TAR_%s=%lo", tar_var[idx], val);
+	xputenv(env[idx]);
+}
+
+void FAST_FUNC data_extract_to_command(archive_handle_t *archive_handle)
+{
+	file_header_t *file_header = archive_handle->file_header;
+
+#if ENABLE_FEATURE_TAR_SELINUX
+	char *sctx = archive_handle->tar__next_file_sctx;
+	if (!sctx)
+		sctx = archive_handle->tar__global_sctx;
+	if (sctx) { /* setfscreatecon is 4 syscalls, avoid if possible */
+		setfscreatecon(sctx);
+		free(archive_handle->tar__next_file_sctx);
+		archive_handle->tar__next_file_sctx = NULL;
+	}
+#endif
+
+	if ((file_header->mode & S_IFMT) == S_IFREG) {
+		pid_t pid;
+		int p[2], status;
+		void (*saved_sigpipe)(int);
+		char *tar_env[TAR_MAX];
+		static const char sh[] = "/bin/sh";
+
+		xpipe(p);
+		saved_sigpipe = signal(SIGPIPE, SIG_IGN);
+		pid = BB_MMU ? fork() : vfork();
+		switch (pid) {
+		case -1:
+			bb_perror_msg_and_die("fork");
+		case 0:
+			/* Child */
+			xdup2(p[0], STDIN_FILENO);
+			close(p[1]);
+
+			str2env(tar_env, TAR_FILETYPE, "f");
+			oct2env(tar_env, TAR_MODE, file_header->mode);
+			str2env(tar_env, TAR_FILENAME, file_header->name);
+			str2env(tar_env, TAR_REALNAME, file_header->name);
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+			str2env(tar_env, TAR_UNAME, file_header->tar__uname);
+			str2env(tar_env, TAR_GNAME, file_header->tar__gname);
+#endif
+			dec2env(tar_env, TAR_SIZE, file_header->size);
+			dec2env(tar_env, TAR_UID, file_header->uid);
+			dec2env(tar_env, TAR_GID, file_header->gid);
+
+			execl(sh, sh + 5, "-c", archive_handle->tar__to_command, NULL);
+
+			bb_perror_msg_and_die("can't run '%s'", archive_handle->tar__to_command);
+		}
+		close(p[0]);
+		bb_copyfd_exact_size(archive_handle->src_fd, p[1], file_header->size);
+		close(p[1]);
+		signal(SIGPIPE, saved_sigpipe);
+
+		while (wait(&status) == -1)
+			if (errno != EINTR)
+				bb_perror_msg_and_die("wait");
+		if (WIFEXITED(status) && WEXITSTATUS(status))
+			bb_error_msg_and_die("'%s' returned status %d",
+				archive_handle->tar__to_command, WEXITSTATUS(status));
+		if (WIFSIGNALED(status))
+			bb_error_msg_and_die("'%s' terminated on signal %d",
+				archive_handle->tar__to_command, WTERMSIG(status));
+
+		if (!BB_MMU) {
+			int i;
+
+			for (i = 0; i < TAR_MAX; i++) {
+				bb_unsetenv(tar_env[i]);
+				free(tar_env[i]);
+			}
+		}
+	}
+
+#if ENABLE_FEATURE_TAR_SELINUX
+	if (sctx)
+		/* reset the context after creating an entry */
+		setfscreatecon(NULL);
+#endif
+}


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