251 lines
9.1 KiB
Diff
251 lines
9.1 KiB
Diff
From 40cd25147b4461979c0d992299f2c101f9034f7a Mon Sep 17 00:00:00 2001
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From: Bernhard Voelker <mail@bernhard-voelker.de>
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Date: Tue, 6 Jun 2017 08:19:29 +0200
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Subject: [PATCH 101/224] xargs: add -o, --open-tty option
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This option is available in the xargs implementation of FreeBSD, NetBSD,
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OpenBSD and in the Apple variant. Add it for compatibility.
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* xargs/xargs.c (open_tty): Add static flag for the new option.
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(longopts): Add member.
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(main): Handle the 'o' case in the getopt_long() loop.
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(prep_child_for_exec): Redirect stdin of the child to /dev/tty when
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the -o option is given. Furthermore, move the just-opened file
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descriptor to STDIN_FILENO.
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(usage): Document the new option.
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* bootstrap.conf (gnulib_modules): Add dup2.
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* xargs/xargs.1 (SYNOPSIS): Replace the too-long list of options by
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"[options]" - they are listed later anyway.
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(OPTIONS): Document the new option.
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(STANDARDS CONFORMANCE): Mention that the -o option is an extension.
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* doc/find.texi (xargs options): Document the new option.
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(Invoking the shell from xargs): Amend the explanation of the
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redirection example with a note about the -o option.
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(Viewing And Editing): Likewise.
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(Error Messages From xargs): Add the message when dup2() fails.
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(NEWS): Mention the new option.
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Fixes http://savannah.gnu.org/bugs/?51151
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---
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NEWS | 4 ++++
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bootstrap.conf | 1 +
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doc/find.texi | 24 ++++++++++++++++++++++++
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xargs/xargs.1 | 41 +++++++++++++----------------------------
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xargs/xargs.c | 33 ++++++++++++++++++++++++++-------
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5 files changed, 68 insertions(+), 35 deletions(-)
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diff --git a/doc/find.texi b/doc/find.texi
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index 24d8ef99..4516b64c 100644
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--- a/doc/find.texi
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+++ b/doc/find.texi
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@@ -3746,6 +3746,17 @@ Use at most @var{max-args} arguments per command line. Fewer than
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option) is exceeded, unless the @samp{-x} option is given, in which
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case @code{xargs} will exit.
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+@item --open-tty
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+@itemx -o
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+Reopen stdin as @file{/dev/tty} in the child process before executing
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+the command, thus allowing that command to be associated to the terminal
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+while @code{xargs} reads from a different stream, e.g. from a pipe.
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+This is useful if you want @code{xargs} to run an interactive application.
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+@example
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+grep -lz PATTERN * | xargs -0o vi
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+@end example
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+
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+
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@item --interactive
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@itemx -p
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Prompt the user about whether to run each command line and read a line
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@@ -3877,6 +3888,10 @@ Therefore instead of keeping a @code{sh} process around for no reason,
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we just arrange for the subshell to exec Emacs, saving an extra
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process creation.
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+Although GNU @code{xargs} and the implementations on some other platforms
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+like BSD support the @samp{-o} option to achieve the same, the above is
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+the portable way to redirect stdin to @file{/dev/tty}.
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+
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Sometimes, though, it can be helpful to keep the shell process around:
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@example
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@@ -4050,6 +4065,10 @@ protect the @code{$@@} against expansion by your interactive shell
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nothing). The capitalised @samp{Emacs} on the command line is used as
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@code{$0} by the shell that @code{xargs} launches.
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+Please note that the implementations in GNU @code{xargs} and at least BSD
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+support the @samp{-o} option as extension to achieve the same, while the
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+above is the portable way to redirect stdin to @file{/dev/tty}.
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+
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@node Archiving
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@section Archiving
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@@ -5564,6 +5583,11 @@ signals to increase or decrease the parallelism of its processing.
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If you don't plan to send it those signals, this warning can be ignored
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(though if you're a programmer, you may want to help us figure out
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why @code{xargs} is confused by your operating system).
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+
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+@item failed to redirect standard input of the child process
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+@code{xargs} redirects the stdin stream of the command to be run to either
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+@file{/dev/null} or to @file{/dev/tty} for the @samp{-o} option.
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+See the manual of the system call @code{dup2(2)}.
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@end table
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@node Error Messages From locate
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diff --git a/xargs/xargs.1 b/xargs/xargs.1
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index 68377868..f66dbc05 100644
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--- a/xargs/xargs.1
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+++ b/xargs/xargs.1
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@@ -4,34 +4,7 @@ xargs \- build and execute command lines from standard input
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.SH SYNOPSIS
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.B xargs
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.nh
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-[\fB\-0prtx\fR]
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-[\fB\-E \fIeof-str\fR]
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-[\fB\-e\fR[\fIeof-str\fR]]
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-[\fB\-\-eof\fR[=\fIeof-str\fR]]
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-[\fB\-\-null\fR]
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-[\fB\-d \fIdelimiter\fR]
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-[\fB\-\-delimiter \fIdelimiter\fR]
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-[\fB\-I \fIreplace-str\fR]
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-[\fB\-i\fR[\fIreplace-str\fR]]
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-[\fB\-\-replace\fR[=\fIreplace-str\fR]]
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-[\fB\-l\fR[\fImax-lines\fR]]
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-[\fB\-L \fImax-lines\fR]
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-[\fB\-\-max\-lines\fR[=\fImax-lines\fR]]
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-[\fB\-n \fImax-args\fR]
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-[\fB\-\-max\-args\fR=\fImax-args\fR]
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-[\fB\-s \fImax-chars\fR]
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-[\fB\-\-max\-chars\fR=\fImax-chars\fR]
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-[\fB\-P \fImax-procs\fR]
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-[\fB\-\-max\-procs\fR=\fImax-procs\fR]
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-[\fB\-\-process\-slot\-var\fR=\fIname\fR]
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-[\fB\-\-interactive\fR]
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-[\fB\-\-verbose\fR]
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-[\fB\-\-exit\fR]
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-[\fB\-\-no\-run\-if\-empty\fR]
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-[\fB\-\-arg\-file\fR=\fIfile\fR]
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-[\fB\-\-show\-limits\fR]
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-[\fB\-\-version\fR]
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-[\fB\-\-help\fR]
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+[\fIoptions\fR]
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[\fIcommand\fR [\fIinitial-arguments\fR]]
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.hy
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.SH DESCRIPTION
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@@ -252,6 +225,15 @@ arrange for each process to produce a separate output file (or
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otherwise use separate resources).
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.TP
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.PD
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+.B \-o, \-\-open\-tty
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+Reopen stdin as
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+.I /dev/tty
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+in the child process before executing the command. This is useful if
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+you want
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+.B xargs
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+to run an interactive application.
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+.TP
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+.PD
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.B \-p, \-\-interactive
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Prompt the user about whether to run each command line and read a line
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from the terminal. Only run the command line if the response starts
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@@ -404,6 +386,9 @@ The \-l and \-i options appear in the 1997 version of the POSIX
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standard, but do not appear in the 2004 version of the standard.
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Therefore you should use \-L and \-I instead, respectively.
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.P
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+The \-o option is an extension to the POSIX standard for better
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+compatibility with BSD.
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+.P
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The POSIX standard allows implementations to have a limit on the size
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of arguments to the
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.B exec
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diff --git a/xargs/xargs.c b/xargs/xargs.c
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index 5cf8c131..a2917e48 100644
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--- a/xargs/xargs.c
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+++ b/xargs/xargs.c
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@@ -151,6 +151,9 @@ static volatile int child_error = EXIT_SUCCESS;
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static volatile int original_exit_value;
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+/* If true, open /dev/tty in the child process before executing the command. */
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+static bool open_tty = false; /* option -o */
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+
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/* If true, print each command on stderr before executing it. */
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static bool print_command = false; /* Option -t */
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@@ -185,6 +188,7 @@ static struct option const longopts[] =
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{"replace", optional_argument, NULL, 'I'},
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{"max-lines", optional_argument, NULL, 'l'},
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{"max-args", required_argument, NULL, 'n'},
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+ {"open-tty", no_argument, NULL, 'o'},
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{"interactive", no_argument, NULL, 'p'},
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{"no-run-if-empty", no_argument, NULL, 'r'},
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{"max-chars", required_argument, NULL, 's'},
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@@ -509,7 +513,7 @@ main (int argc, char **argv)
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bc_use_sensible_arg_max (&bc_ctl);
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}
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- while ((optc = getopt_long (argc, argv, "+0a:E:e::i::I:l::L:n:prs:txP:d:",
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+ while ((optc = getopt_long (argc, argv, "+0a:E:e::i::I:l::L:n:oprs:txP:d:",
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longopts, &option_index)) != -1)
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{
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switch (optc)
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@@ -608,6 +612,10 @@ main (int argc, char **argv)
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bc_ctl.exit_if_size_exceeded = true;
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break;
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+ case 'o':
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+ open_tty = true;
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+ break;
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+
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case 'p':
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query_before_executing = true;
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print_command = true;
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@@ -1185,22 +1193,30 @@ prep_child_for_exec (void)
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unsigned int slot = add_proc (0);
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set_slot_var (slot);
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- if (!keep_stdin)
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+ if (!keep_stdin || open_tty)
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{
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- const char inputfile[] = "/dev/null";
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- /* fprintf (stderr, "attaching stdin to /dev/null\n"); */
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+ int fd;
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+ const char *inputfile = open_tty ? "/dev/tty" : "/dev/null";
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close (0);
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- if (open (inputfile, O_RDONLY) < 0)
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+ if ((fd = open (inputfile, O_RDONLY)) < 0)
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{
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- /* This is not entirely fatal, since
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+ /* Treat a failure to open /dev/tty as fatal.
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+ * The other case is not entirely fatal, since
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* executing the child with a closed
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* stdin is almost as good as executing it
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* with its stdin attached to /dev/null.
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*/
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- error (0, errno, "%s",
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+ error (open_tty ? EXIT_FAILURE : 0, errno, "%s",
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quotearg_n_style (0, locale_quoting_style, inputfile));
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}
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+ if (STDIN_FILENO < fd)
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+ {
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+ if (dup2(fd, STDIN_FILENO) != 0)
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+ error (EXIT_FAILURE, errno,
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+ _("failed to redirect standard input of the child process"));
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+ close(fd);
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+ }
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}
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}
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@@ -1676,6 +1692,9 @@ usage (int status)
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HTL (_(" -l[MAX-LINES] similar to -L but defaults to at most one non-\n"
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" blank input line if MAX-LINES is not specified\n"));
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HTL (_(" -n, --max-args=MAX-ARGS use at most MAX-ARGS arguments per command line\n"));
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+ HTL (_(" -o, --open-tty Reopen stdin as /dev/tty in the child process\n"
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+ " before executing the command; useful to run an\n"
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+ " interactive application.\n"));
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HTL (_(" -P, --max-procs=MAX-PROCS run at most MAX-PROCS processes at a time\n"));
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HTL (_(" -p, --interactive prompt before running commands\n"));
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HTL (_(" --process-slot-var=VAR set environment variable VAR in child processes\n"));
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--
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2.19.1
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