Re: [Help-tar] Global header contents as environment variables of the external program called with --to-command option

[Sergey Poznyakoff]

<address@hidden> ha escrit:

> It would be nice to have saved keyword-values as a variables in the
> environment of that <external_program> (like other stuff: TAR_MTIME,
> TAR_ATIME,...).
> Is it real? 

Yes, it is possible.  Please try the attached patch (built against
current git HEAD).

Regards,
Sergey

>From 5bdf1f93ce98a46475b5e1ad3db0a9f3b4dbaa44 Mon Sep 17 00:00:00 2001
From: Sergey Poznyakoff <address@hidden>
Date: Tue, 25 Feb 2014 16:16:36 +0200
Subject: [PATCH] Pass extended global headers to the environment of
 --to-command and --checkpoint

* NEWS: Update.
* doc/tar.1: Document TAR_HEADER_ envars.
* doc/tar.texi: Likewise.
* src/common.h (xheader_iterate_global): New prototype.
* src/system.c (stat_to_env): Call xheader_iterate_global
to pass global headers to the environment.
* src/xheader.c (xheader_iterate_global): New function.
---
 NEWS          | 11 +++++++++--
 doc/tar.1     | 13 +++++++++++--
 doc/tar.texi  | 14 ++++++++++++++
 src/common.h  |  1 +
 src/system.c  | 13 +++++++++++++
 src/xheader.c | 10 ++++++++++
 6 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index fa24142..48670ae 100644
--- a/NEWS
+++ b/NEWS
@@ -1,4 +1,4 @@
-GNU tar NEWS - User visible changes. 2014-02-21
+GNU tar NEWS - User visible changes. 2014-02-25
 Please send GNU tar bug reports to <address@hidden>

 
@@ -67,7 +67,14 @@ speed up archivation.
 This release includes official tar(1) and rmt(8) manpages.
 Distribution maintainers are kindly asked to use these instead of the
 home-made pages they provided so far.
-
+
+* Environment variables for --to-command and --checkpoint options
+
+In addition to existing tar-specific environment variables, each
+global extended header from a PAX archive is converted to a
+corresponding variable whose name is constructed by concatenating the
+string "TAR_HEADER_" and the original header name.
+
 
 version 1.27.1 - Sergey Poznyakoff, 2013-11-17

diff --git a/doc/tar.1 b/doc/tar.1
index cd133d9..647f914 100644
--- a/doc/tar.1
+++ b/doc/tar.1
@@ -13,7 +13,7 @@
 .\"
 .\" You should have received a copy of the GNU General Public License
 .\" along with this program.  If not, see <http://www.gnu.org/licenses/>.
-.TH TAR 1 "February 22, 2014" "TAR" "GNU TAR Manual"
+.TH TAR 1 "February 25, 2014" "TAR" "GNU TAR Manual"
 .SH NAME
 tar \- an archiving utility
 .SH SYNOPSIS
@@ -448,9 +448,18 @@ Format of the archive being processed.  One of:
 .BR posix ,
 .BR ustar ,
 .BR v7 .
+.TP
 .B TAR_SUBCOMMAND
 A short option (with a leading dash) describing the operation \fBtar\fR is
-executing.
+executing.
+.TP
+\fBTAR_HEADER_\fINAME\fR
+When processing a POSIX.1-2001 archive that has global extended
+headers, each header is converted to a corresponding environment
+variable.  The variable name is constructed by concatenating the
+string
+.B TAR_HEADER_
+and the original header name.
 .RE
 .SS Handling of file attributes
 .TP
diff --git a/doc/tar.texi b/doc/tar.texi
index e3df0c9..dd89ef5 100644
--- a/doc/tar.texi
+++ b/doc/tar.texi
@@ -4194,6 +4194,13 @@ A short option describing the operation @command{tar} is 
executing.
 @item TAR_FORMAT
 Format of the archive being processed. @xref{Formats}, for a complete
 list of archive format names.
+
address@hidden address@hidden, checkpoint script environment
address@hidden address@hidden
+When processing a POSIX.1-2001 archive (@pxref{posix}) that has global
+extended headers, each header is converted to a corresponding
+environment variable.  The variable name is constructed by
+concatenating the string @samp{TAR_HEADER_} and the original header name.
 @end table

 These environment variables can also be passed as arguments to the
@@ -5776,6 +5783,13 @@ Ordinal number of the volume @command{tar} is processing.
 @item TAR_FORMAT
 Format of the archive being processed. @xref{Formats}, for a complete
 list of archive format names.
+
address@hidden address@hidden, to-command environment
address@hidden address@hidden
+When processing a POSIX.1-2001 archive (@pxref{posix}) that has global
+extended headers, each header is converted to a corresponding
+environment variable.  The variable name is constructed by
+concatenating the string @samp{TAR_HEADER_} and the original header name.
 @end table

 These variables are defined prior to executing the command, so you can
diff --git a/src/common.h b/src/common.h
index edf787c..7269a48 100644
--- a/src/common.h
+++ b/src/common.h
@@ -784,6 +784,7 @@ void update_archive (void);

 void xheader_decode (struct tar_stat_info *stat);
 void xheader_decode_global (struct xheader *xhdr);
+void xheader_iterate_global (int (*fn) (const char *, const char *));
 void xheader_store (char const *keyword, struct tar_stat_info *st,
                    void const *data);
 void xheader_read (struct xheader *xhdr, union block *header, off_t size);
diff --git a/src/system.c b/src/system.c
index 9414233..d93fd46 100644
--- a/src/system.c
+++ b/src/system.c
@@ -672,6 +672,17 @@ chr_to_env (char const *envar, char c)
     xalloc_die ();
 }

+#define XHDR_PFX_S "TAR_HEADER_"
+
+static int
+hdr_to_env (const char *kw, const char *value)
+{
+  char *var = xasprintf ("%s%s", XHDR_PFX_S, kw);
+  str_to_env (var, value);
+  free (var);
+  return 0;
+}
+
 static void
 stat_to_env (char *name, char type, struct tar_stat_info *st)
 {
@@ -695,6 +706,8 @@ stat_to_env (char *name, char type, struct tar_stat_info 
*st)
   dec_to_env ("TAR_UID", st->stat.st_uid);
   dec_to_env ("TAR_GID", st->stat.st_gid);

+  xheader_iterate_global (hdr_to_env);
+
   switch (type)
     {
     case 'b':
diff --git a/src/xheader.c b/src/xheader.c
index c94c6d3..43c8665 100644
--- a/src/xheader.c
+++ b/src/xheader.c
@@ -782,6 +782,16 @@ xheader_decode_global (struct xheader *xhdr)
     }
 }

+void
+xheader_iterate_global (int (*fn) (const char *, const char *))
+{
+  struct keyword_list *kp;
+  for (kp = global_header_override_list; kp; kp = kp->next)
+    if (fn (kp->pattern, kp->value))
+      break;
+}
+
+
 static void
 xheader_init (struct xheader *xhdr)
 {
--
1.7.12.1