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Fadi Moukayed
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‎CMakeLists.txt‎

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cmake_minimum_required(VERSION 3.9)
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project(bashext-socket VERSION 1.0 DESCRIPTION "BASH socket extension" LANGUAGES C)
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include(GNUInstallDirs)
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set(DEFAULT_BUILD_TYPE "Release")
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find_package(PkgConfig REQUIRED)
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pkg_check_modules(BASH REQUIRED IMPORTED_TARGET bash)
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add_library(bashext-socket SHARED
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src/accept.c
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src/socket.c
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src/alarm.c
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src/pause.c)
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set_target_properties(bashext-socket PROPERTIES
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VERSION ${PROJECT_VERSION} SOVERSION 1)
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target_link_libraries(bashext-socket PUBLIC PkgConfig::BASH)
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install(TARGETS bashext-socket
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LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

‎README.md‎

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# bash-socket
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Loadable BASH extension for socket programming
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# bash-extensions
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Loadable BASH extensions for socket programming.
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## Loading the extension
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`$ enable -f /usr/lib/x86_64-linux-gnu/libbashext-socket.so accept socket alarm pause`
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## Provided functions
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The extension provides the following functions
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### accept(2)
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```
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$ help accept
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accept: accept varname [socket]
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accept a connection on a socket.
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Calls accept(2) on the given socket. The resulting file descriptor
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is written to the variable denoted by varname.
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if socket is not given, assumes 0 (STDIN).
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```
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### socket(2)
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```
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$ help socket
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socket: socket varname AF_UNIX|AF_INET|AF_INET6 SOCK_STREAM|SOCK_DGRAM local|peer PATH|ADDRESS [port] [queue]
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creates a socket.
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Provides an interface for creating and using POSIX sockets
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The result socket handle is written to the variable denoted by varname.
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```
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### alarm(2)
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```
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$ help alarm
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alarm: alarm seconds [varname]
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Arranges for a SIGALRM to be delivered to the shell in seconds.
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If seconds is zero, any pending alarm is cancelled.
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If varname is given, it is set to the number of seconds remaining until any
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previously scheduled alarm was to be delivered, or zero if there was
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previously scheduled alarm.
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```
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### pause(2)
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```
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$ help pause
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pause: pause
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Suspends the shell until a signal is delivered.
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```
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## Examples
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### Forking AF\_UNIX server
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Code (`echo-server.sh`):
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```
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#!/bin/bash
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set -eu
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enable -f "/usr/lib/$HOSTTYPE-$OSTYPE/libbashext-socket.so" socket accept
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socket SOCK AF_UNIX SOCK_STREAM local "$1"
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trap "trap - TERM && kill -- -$$ 2>/dev/null" INT TERM HUP QUIT EXIT
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while accept FD "${SOCK}" 2>/dev/null
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do
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while read -r DATA
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do
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printf '%s\n' "${DATA}"
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done <&${FD} >&${FD} &
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exec {FD}>&-
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wait
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done
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```
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Demo:
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```
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$ bash socket-server.sh /tmp/sock &
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[1] 31281
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$ nc -N -U /tmp/sock <<< "Hello World"
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Hello World
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```
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### Simple AF\_UNIX client
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Code (`echo-client.sh`)
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```
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#!/bin/bash
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set -eu
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enable -f "/usr/lib/$HOSTTYPE-$OSTYPE/libbashext-socket.so" socket
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socket SOCK AF_UNIX SOCK_STREAM peer "$1"
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echo "Hello World!" >&${SOCK}
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read -r -u ${SOCK} REPLY
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echo "$REPLY"
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```
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Demo:
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```
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$ bash echo-server.sh /tmp/sock &
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[1] 12991
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$ bash echo-client.sh /tmp/sock
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Hello World!
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```

‎debian/changelog‎

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bash-ext-socket (1.0-1) unstable; urgency=medium
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* Initial release
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-- Fadi Moukayed <fadi.moukayed@rohde-schwarz.com> Sat, 04 Apr 2020 14:23:28 +0000

‎debian/control‎

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Source: bash-ext-socket
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Priority: optional
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Maintainer: Fadi Moukayed <fadi.moukayed@rohde-schwarz.com>
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Build-Depends: debhelper-compat (= 11), cmake, bash-builtins
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Standards-Version: 4.1.2
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Section: shells
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Package: bash-ext-socket
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Architecture: any
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Multi-Arch: same
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Depends: ${shlibs:Depends}, ${misc:Depends}
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Description: BASH socket accept(3) extension
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This C extension provides an "accept"-builtin function, allowing BASH program to utilize socket file handles.

‎debian/copyright‎

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Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
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Upstream-Name: bash-ext-socket
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Files: *
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Copyright: 2020 Fadi Moukayed <fadi.moukayed@rohde-schwarz.com>
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License: MIT
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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.
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The above copyright notice and this permission notice (including the next
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paragraph) shall be included in all copies or substantial portions of the
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Software.
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.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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DEALINGS IN THE SOFTWARE.
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Files: debian/*
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Copyright: 2020 Fadi Moukayed <fadi.moukayed@rohde-schwarz.com>
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License: MIT
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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.
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The above copyright notice and this permission notice (including the next
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paragraph) shall be included in all copies or substantial portions of the
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Software.
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.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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DEALINGS IN THE SOFTWARE.

‎debian/rules‎

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#!/usr/bin/make -f
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%:
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dh $@

‎src/accept.c‎

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#include "builtins.h"
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#include "config.h"
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#include "shell.h"
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#include "common.h"
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#include <errno.h>
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#include <stdio.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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static int
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accept_builtin(WORD_LIST *list)
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{
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if (list == NULL) {
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builtin_usage();
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return EX_USAGE;
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}
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if (no_options(list)) {
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return EX_USAGE;
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}
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const char *varname = list->word->word;
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list = list->next;
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/* Default to STDIN */
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int socket = 0;
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/* Pick up socket file descriptor from argument if specified. */
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if (list != NULL) {
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if (sscanf(list->word->word, "%d", &socket) < 1) {
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builtin_error("invalid socket fd: %s", list->word->word);
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return EXECUTION_FAILURE;
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}
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list = list->next;
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}
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if (list != NULL) {
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builtin_usage();
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return EX_USAGE;
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}
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int accfd = accept(socket, NULL, NULL);
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if (accfd == -1) {
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builtin_error("%s", strerror(errno));
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return EXECUTION_FAILURE;
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}
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/* Bind file description number to varname. */
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char buffer[32];
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int ret = snprintf(buffer, sizeof(buffer), "%d", accfd);
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if (ret < 0 || ((unsigned int)ret) >= sizeof(buffer)) {
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builtin_error("snprintf: %s", strerror(errno));
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return EXECUTION_FAILURE;
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}
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bind_variable(varname, buffer, 0);
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return EXECUTION_SUCCESS;
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}
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static char *const accept_doc[] = {
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"accept a connection on a socket.",
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"Calls accept(2) on the given socket. The resulting file descriptor",
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"is written to the variable denoted by varname.",
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"if socket is not given, assumes 0 (STDIN).", NULL
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};
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struct builtin accept_struct = {
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.name = "accept",
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.function = accept_builtin,
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.flags = BUILTIN_ENABLED,
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.long_doc = accept_doc,
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.short_doc = "accept varname [socket]",
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.handle = NULL
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};

‎src/alarm.c‎

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#include "builtins.h"
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#include "config.h"
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#include "shell.h"
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#include "common.h"
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#include <errno.h>
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#include <stdio.h>
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#include <unistd.h>
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static int
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alarm_builtin(WORD_LIST *list)
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{
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if (list == NULL) {
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builtin_usage();
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return EX_USAGE;
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}
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if (no_options(list)) {
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return EX_USAGE;
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}
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unsigned int seconds;
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if (sscanf(list->word->word, "%u", &seconds) != 1) {
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builtin_error("invalid argument: %s", list->word->word);
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return EXECUTION_FAILURE;
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}
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list = list->next;
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unsigned int remaining = alarm(seconds);
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if (list != NULL) {
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char buffer[16];
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int ret = snprintf(buffer, sizeof(buffer), "%u", remaining);
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if (ret < 0 || ((unsigned int)ret) >= sizeof(buffer)) {
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builtin_warning("snprintf: %s", strerror(errno));
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} else {
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bind_variable(list->word->word, buffer, 0);
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}
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}
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return EXECUTION_SUCCESS;
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}
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static char *const alarm_doc[] = {
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"Arranges for a SIGALRM to be delivered to the shell in seconds.",
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"If seconds is zero, any pending alarm is cancelled.",
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"If varname is given, it is set to the number of seconds remaining until any",
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"previously scheduled alarm was to be delivered, or zero if there was",
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"no previously scheduled alarm.", NULL
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};
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struct builtin alarm_struct = {
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.name = "alarm",
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.function = alarm_builtin,
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.flags = BUILTIN_ENABLED,
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.long_doc = alarm_doc,
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.short_doc = "alarm seconds [varname]",
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.handle = NULL
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};

‎src/pause.c‎

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#include "builtins.h"
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#include "config.h"
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#include "shell.h"
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#include "common.h"
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#include <unistd.h>
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static int
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pause_builtin(WORD_LIST *list)
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{
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if (no_options(list)) {
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return EX_USAGE;
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}
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/* Don't accept any arguments. */
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if (list != NULL) {
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builtin_usage();
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return EX_USAGE;
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}
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(void)pause();
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return EXECUTION_SUCCESS;
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}
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static char *const pause_doc[] = {
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"Suspends the shell until a signal is delivered.", NULL
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};
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struct builtin pause_struct = {
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.name = "pause",
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.function = pause_builtin,
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.flags = BUILTIN_ENABLED,
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.long_doc = pause_doc,
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.short_doc = "pause",
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.handle = NULL
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};

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