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authorBernhard Voelker <mail@bernhard-voelker.de>2017-06-06 08:19:29 +0200
committerBernhard Voelker <mail@bernhard-voelker.de>2017-06-09 00:44:42 +0200
commit40cd25147b4461979c0d992299f2c101f9034f7a (patch)
tree451d616a667db9356fd37a58e95d3bc6783b660c
parent6dfd05ca58e42ada04780f2f74383c6e54bcabba (diff)
downloadfindutils-40cd25147b.tar.gz
xargs: add -o, --open-tty option
This option is available in the xargs implementation of FreeBSD, NetBSD, OpenBSD and in the Apple variant. Add it for compatibility. * xargs/xargs.c (open_tty): Add static flag for the new option. (longopts): Add member. (main): Handle the 'o' case in the getopt_long() loop. (prep_child_for_exec): Redirect stdin of the child to /dev/tty when the -o option is given. Furthermore, move the just-opened file descriptor to STDIN_FILENO. (usage): Document the new option. * bootstrap.conf (gnulib_modules): Add dup2. * xargs/xargs.1 (SYNOPSIS): Replace the too-long list of options by "[options]" - they are listed later anyway. (OPTIONS): Document the new option. (STANDARDS CONFORMANCE): Mention that the -o option is an extension. * doc/find.texi (xargs options): Document the new option. (Invoking the shell from xargs): Amend the explanation of the redirection example with a note about the -o option. (Viewing And Editing): Likewise. (Error Messages From xargs): Add the message when dup2() fails. (NEWS): Mention the new option. Fixes http://savannah.gnu.org/bugs/?51151
-rw-r--r--NEWS4
-rw-r--r--bootstrap.conf1
-rw-r--r--doc/find.texi24
-rw-r--r--xargs/xargs.141
-rw-r--r--xargs/xargs.c33
5 files changed, 68 insertions, 35 deletions
diff --git a/NEWS b/NEWS
index 3dd230d..91c0b95 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,10 @@ of the - yet more portable - '( -type l -o -type d )'.
find now diagnoses failures returned by readdir(). This bug was inherent
in the use of FTS.
+xargs now supports the -o, --open-tty option to reopen stdin as /dev/tty
+in the child process before executing the command; useful to run an
+interactive application. Added for compatibility with BSD.
+
** Documentation Changes
Some minor documentation improvements are listed in "Bug Fixes" below.
diff --git a/bootstrap.conf b/bootstrap.conf
index bf44f80..07831aa 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -87,6 +87,7 @@ gnulib_modules="
d-type
dirent-safer
dirname
+ dup2
errno
error
faccessat
diff --git a/doc/find.texi b/doc/find.texi
index 24d8ef9..4516b64 100644
--- a/doc/find.texi
+++ b/doc/find.texi
@@ -3746,6 +3746,17 @@ Use at most @var{max-args} arguments per command line. Fewer than
option) is exceeded, unless the @samp{-x} option is given, in which
case @code{xargs} will exit.
+@item --open-tty
+@itemx -o
+Reopen stdin as @file{/dev/tty} in the child process before executing
+the command, thus allowing that command to be associated to the terminal
+while @code{xargs} reads from a different stream, e.g. from a pipe.
+This is useful if you want @code{xargs} to run an interactive application.
+@example
+grep -lz PATTERN * | xargs -0o vi
+@end example
+
+
@item --interactive
@itemx -p
Prompt the user about whether to run each command line and read a line
@@ -3877,6 +3888,10 @@ Therefore instead of keeping a @code{sh} process around for no reason,
we just arrange for the subshell to exec Emacs, saving an extra
process creation.
+Although GNU @code{xargs} and the implementations on some other platforms
+like BSD support the @samp{-o} option to achieve the same, the above is
+the portable way to redirect stdin to @file{/dev/tty}.
+
Sometimes, though, it can be helpful to keep the shell process around:
@example
@@ -4050,6 +4065,10 @@ protect the @code{$@@} against expansion by your interactive shell
nothing). The capitalised @samp{Emacs} on the command line is used as
@code{$0} by the shell that @code{xargs} launches.
+Please note that the implementations in GNU @code{xargs} and at least BSD
+support the @samp{-o} option as extension to achieve the same, while the
+above is the portable way to redirect stdin to @file{/dev/tty}.
+
@node Archiving
@section Archiving
@@ -5564,6 +5583,11 @@ signals to increase or decrease the parallelism of its processing.
If you don't plan to send it those signals, this warning can be ignored
(though if you're a programmer, you may want to help us figure out
why @code{xargs} is confused by your operating system).
+
+@item failed to redirect standard input of the child process
+@code{xargs} redirects the stdin stream of the command to be run to either
+@file{/dev/null} or to @file{/dev/tty} for the @samp{-o} option.
+See the manual of the system call @code{dup2(2)}.
@end table
@node Error Messages From locate
diff --git a/xargs/xargs.1 b/xargs/xargs.1
index 6837786..f66dbc0 100644
--- a/xargs/xargs.1
+++ b/xargs/xargs.1
@@ -4,34 +4,7 @@ xargs \- build and execute command lines from standard input
.SH SYNOPSIS
.B xargs
.nh
-[\fB\-0prtx\fR]
-[\fB\-E \fIeof-str\fR]
-[\fB\-e\fR[\fIeof-str\fR]]
-[\fB\-\-eof\fR[=\fIeof-str\fR]]
-[\fB\-\-null\fR]
-[\fB\-d \fIdelimiter\fR]
-[\fB\-\-delimiter \fIdelimiter\fR]
-[\fB\-I \fIreplace-str\fR]
-[\fB\-i\fR[\fIreplace-str\fR]]
-[\fB\-\-replace\fR[=\fIreplace-str\fR]]
-[\fB\-l\fR[\fImax-lines\fR]]
-[\fB\-L \fImax-lines\fR]
-[\fB\-\-max\-lines\fR[=\fImax-lines\fR]]
-[\fB\-n \fImax-args\fR]
-[\fB\-\-max\-args\fR=\fImax-args\fR]
-[\fB\-s \fImax-chars\fR]
-[\fB\-\-max\-chars\fR=\fImax-chars\fR]
-[\fB\-P \fImax-procs\fR]
-[\fB\-\-max\-procs\fR=\fImax-procs\fR]
-[\fB\-\-process\-slot\-var\fR=\fIname\fR]
-[\fB\-\-interactive\fR]
-[\fB\-\-verbose\fR]
-[\fB\-\-exit\fR]
-[\fB\-\-no\-run\-if\-empty\fR]
-[\fB\-\-arg\-file\fR=\fIfile\fR]
-[\fB\-\-show\-limits\fR]
-[\fB\-\-version\fR]
-[\fB\-\-help\fR]
+[\fIoptions\fR]
[\fIcommand\fR [\fIinitial-arguments\fR]]
.hy
.SH DESCRIPTION
@@ -252,6 +225,15 @@ arrange for each process to produce a separate output file (or
otherwise use separate resources).
.TP
.PD
+.B \-o, \-\-open\-tty
+Reopen stdin as
+.I /dev/tty
+in the child process before executing the command. This is useful if
+you want
+.B xargs
+to run an interactive application.
+.TP
+.PD
.B \-p, \-\-interactive
Prompt the user about whether to run each command line and read a line
from the terminal. Only run the command line if the response starts
@@ -404,6 +386,9 @@ The \-l and \-i options appear in the 1997 version of the POSIX
standard, but do not appear in the 2004 version of the standard.
Therefore you should use \-L and \-I instead, respectively.
.P
+The \-o option is an extension to the POSIX standard for better
+compatibility with BSD.
+.P
The POSIX standard allows implementations to have a limit on the size
of arguments to the
.B exec
diff --git a/xargs/xargs.c b/xargs/xargs.c
index 5cf8c13..a2917e4 100644
--- a/xargs/xargs.c
+++ b/xargs/xargs.c
@@ -151,6 +151,9 @@ static volatile int child_error = EXIT_SUCCESS;
static volatile int original_exit_value;
+/* If true, open /dev/tty in the child process before executing the command. */
+static bool open_tty = false; /* option -o */
+
/* If true, print each command on stderr before executing it. */
static bool print_command = false; /* Option -t */
@@ -185,6 +188,7 @@ static struct option const longopts[] =
{"replace", optional_argument, NULL, 'I'},
{"max-lines", optional_argument, NULL, 'l'},
{"max-args", required_argument, NULL, 'n'},
+ {"open-tty", no_argument, NULL, 'o'},
{"interactive", no_argument, NULL, 'p'},
{"no-run-if-empty", no_argument, NULL, 'r'},
{"max-chars", required_argument, NULL, 's'},
@@ -509,7 +513,7 @@ main (int argc, char **argv)
bc_use_sensible_arg_max (&bc_ctl);
}
- while ((optc = getopt_long (argc, argv, "+0a:E:e::i::I:l::L:n:prs:txP:d:",
+ while ((optc = getopt_long (argc, argv, "+0a:E:e::i::I:l::L:n:oprs:txP:d:",
longopts, &option_index)) != -1)
{
switch (optc)
@@ -608,6 +612,10 @@ main (int argc, char **argv)
bc_ctl.exit_if_size_exceeded = true;
break;
+ case 'o':
+ open_tty = true;
+ break;
+
case 'p':
query_before_executing = true;
print_command = true;
@@ -1185,22 +1193,30 @@ prep_child_for_exec (void)
unsigned int slot = add_proc (0);
set_slot_var (slot);
- if (!keep_stdin)
+ if (!keep_stdin || open_tty)
{
- const char inputfile[] = "/dev/null";
- /* fprintf (stderr, "attaching stdin to /dev/null\n"); */
+ int fd;
+ const char *inputfile = open_tty ? "/dev/tty" : "/dev/null";
close (0);
- if (open (inputfile, O_RDONLY) < 0)
+ if ((fd = open (inputfile, O_RDONLY)) < 0)
{
- /* This is not entirely fatal, since
+ /* Treat a failure to open /dev/tty as fatal.
+ * The other case is not entirely fatal, since
* executing the child with a closed
* stdin is almost as good as executing it
* with its stdin attached to /dev/null.
*/
- error (0, errno, "%s",
+ error (open_tty ? EXIT_FAILURE : 0, errno, "%s",
quotearg_n_style (0, locale_quoting_style, inputfile));
}
+ if (STDIN_FILENO < fd)
+ {
+ if (dup2(fd, STDIN_FILENO) != 0)
+ error (EXIT_FAILURE, errno,
+ _("failed to redirect standard input of the child process"));
+ close(fd);
+ }
}
}
@@ -1676,6 +1692,9 @@ usage (int status)
HTL (_(" -l[MAX-LINES] similar to -L but defaults to at most one non-\n"
" blank input line if MAX-LINES is not specified\n"));
HTL (_(" -n, --max-args=MAX-ARGS use at most MAX-ARGS arguments per command line\n"));
+ HTL (_(" -o, --open-tty Reopen stdin as /dev/tty in the child process\n"
+ " before executing the command; useful to run an\n"
+ " interactive application.\n"));
HTL (_(" -P, --max-procs=MAX-PROCS run at most MAX-PROCS processes at a time\n"));
HTL (_(" -p, --interactive prompt before running commands\n"));
HTL (_(" --process-slot-var=VAR set environment variable VAR in child processes\n"));