+Hovewer, @option{--to-command} may be more convenient for use with
+multiple files. See the next section.
+
+@node Writing to an External Program
+@unnumberedsubsubsec Writing to an External Program
+
+You can instruct @command{tar} to send the contents of each extracted
+file to the standard input of an external program:
+
+@table @option
+@item --to-program=@var{command}
+Extract files and pipe their contents to the standard input of
+@var{command}. When this option is used, instead of creating the
+files specified, @command{tar} invokes @var{command} and pipes the
+contents of the files to its standard output. @var{Command} may
+contain command line arguments. The program is executed via
+@code{sh -c}. Notice, that @var{command} is executed once for each regular file
+extracted. Non-regular files (directories, etc.) are ignored when this
+option is used.
+@end table
+
+The command can obtain the information about the file it processes
+from the following environment variables:
+
+@table @var
+@vrindex TAR_FILETYPE, to-command environment
+@item TAR_FILETYPE
+Type of the file. It is a single letter with the following meaning:
+
+@multitable @columnfractions 0.10 0.90
+@item f @tab Regular file
+@item d @tab Directory
+@item l @tab Symbolic link
+@item h @tab Hard link
+@item b @tab Block device
+@item c @tab Character device
+@end multitable
+
+Currently only regular files are supported.
+
+@vrindex TAR_MODE, to-command environment
+@item TAR_MODE
+File mode, an octal number.
+
+@vrindex TAR_FILENAME, to-command environment
+@item TAR_FILENAME
+The name of the file.
+
+@vrindex TAR_REALNAME, to-command environment
+@item TAR_REALNAME
+Name of the file as stored in the archive.
+
+@vrindex TAR_UNAME, to-command environment
+@item TAR_UNAME
+Name of the file owner.
+
+@vrindex TAR_GNAME, to-command environment
+@item TAR_GNAME
+Name of the file owner group.
+
+@vrindex TAR_ATIME, to-command environment
+@item TAR_ATIME
+Time of last access. It is a decimal number, representing seconds
+since the epoch. If the archive provides times with nanosecond
+precision, the nanoseconds are appended to the timestamp after a
+decimal point.
+
+@vrindex TAR_MTIME, to-command environment
+@item TAR_MTIME
+Time of last modification.
+
+@vrindex TAR_CTIME, to-command environment
+@item TAR_CTIME
+Time of last status change.
+
+@vrindex TAR_SIZE, to-command environment
+@item TAR_SIZE
+Size of the file.
+
+@vrindex TAR_UID, to-command environment
+@item TAR_UID
+UID of the file owner.
+
+@vrindex TAR_GID, to-command environment
+@item TAR_GID
+GID of the file owner.
+@end table
+
+In addition to these variables, @env{TAR_VERSION} contains the
+@GNUTAR{} version number.
+
+If @var{command} exits with a non-0 status, @command{tar} will print
+an error message similar to the following:
+
+@smallexample
+tar: 2345: Child returned status 1
+@end smallexample
+
+Here, @samp{2345} is the PID of the finished process.
+
+If this behavior is not wanted, use @option{--ignore-command-error}:
+
+@table @option
+@item --ignore-command-error
+Ignore exit codes of subprocesses. Notice that if the program
+exits on signal or otherwise terminates abnormally, the error message
+will be printed even if this option is used.
+
+@item --no-ignore-command-error
+Cancel the effect of any previous @option{--ignore-command-error}
+option. This option is useful if you have set
+@option{--ignore-command-error} in @env{TAR_OPTIONS}
+(@pxref{TAR_OPTIONS}) and wish to temporarily cancel it.
+@end table
+