374 lines
11 KiB
C
374 lines
11 KiB
C
/*
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Date: Tue, 16 Mar 2004 19:38:40 -0800
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From: Harold Levy <Harold.Levy@synopsys.com>
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Subject: fgets(stdin) --> readline() redirector
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To: chet@po.cwru.edu
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Hi Chet,
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Here is something you may find useful enough to include in the readline
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distribution. It is a shared library that redirects calls to fgets(stdin)
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to readline() via LD_PRELOAD, and it supports a custom prompt and list of
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command names. Many people have asked me for this file, so I thought I'd
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pass it your way in hope of just including it with readline to begin with.
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Best Regards,
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-Harold
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*/
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/******************************************************************************
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*******************************************************************************
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FILE NAME: fgets.c TARGET: libfgets.so
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AUTHOR: Harold Levy VERSION: 1.0
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hlevy@synopsys.com
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ABSTRACT: Customize fgets() behavior via LD_PRELOAD in the following ways:
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-- If fgets(stdin) is called, redirect to GNU readline() to obtain
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command-line editing, file-name completion, history, etc.
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-- A list of commands for command-name completion can be configured by
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setting the environment-variable FGETS_COMMAND_FILE to a file containing
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the list of commands to be used.
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-- Command-line editing with readline() works best when the prompt string
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is known; you can set this with the FGETS_PROMPT environment variable.
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-- There special strings that libfgets will interpret as internal commands:
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_fgets_reset_ reset the command list
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_fgets_dump_ dump status
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_fgets_debug_ toggle debug messages
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HOW TO BUILD: Here are examples of how to build libfgets.so on various
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platforms; you will have to add -I and -L flags to configure access to
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the readline header and library files.
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(32-bit builds with gcc)
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AIX: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldl -lreadline -ltermcap
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HP-UX: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldld -lreadline
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Linux: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldl -lreadline
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SunOS: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldl -lgen -lreadline
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(64-bit builds without gcc)
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SunOS: SUNWspro/bin/cc -D_LARGEFILE64_SOURCE=1 -xtarget=ultra -xarch=v9 \
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-KPIC fgets.c -Bdynamic -lc -ldl -lgen -ltermcap -lreadline
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HOW TO USE: Different operating systems have different levels of support
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for the LD_PRELOAD concept. The generic method for 32-bit platforms is to
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put libtermcap.so, libfgets.so, and libreadline.so (with absolute paths)
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in the LD_PRELOAD environment variable, and to put their parent directories
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in the LD_LIBRARY_PATH environment variable. Unfortunately there is no
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generic method for 64-bit platforms; e.g. for 64-bit SunOS, you would have
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to build both 32-bit and 64-bit libfgets and libreadline libraries, and
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use the LD_FLAGS_32 and LD_FLAGS_64 environment variables with preload and
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library_path configurations (a mix of 32-bit and 64-bit calls are made under
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64-bit SunOS).
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EXAMPLE WRAPPER: Here is an example shell script wrapper around the
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program "foo" that uses fgets() for command-line input:
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#!/bin/csh
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#### replace this with the libtermcap.so directory:
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set dir1 = "/usr/lib"
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#### replace this with the libfgets.so directory:
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set dir2 = "/usr/fgets"
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#### replace this with the libreadline.so directory:
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set dir3 = "/usr/local/lib"
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set lib1 = "${dir1}/libtermcap.so"
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set lib2 = "${dir2}/libfgets.so"
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set lib3 = "${dir3}/libreadline.so"
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if ( "${?LD_PRELOAD}" ) then
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setenv LD_PRELOAD "${lib1}:${lib2}:${lib3}:${LD_PRELOAD}"
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else
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setenv LD_PRELOAD "${lib1}:${lib2}:${lib3}"
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endif
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if ( "${?LD_LIBRARY_PATH}" ) then
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setenv LD_LIBRARY_PATH "${dir1}:${dir2}:${dir3}:${LD_LIBRARY_PATH}"
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else
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setenv LD_LIBRARY_PATH "${dir1}:${dir2}:${dir3}"
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endif
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setenv FGETS_COMMAND_FILE "${dir2}/foo.commands"
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setenv FGETS_PROMPT "foo> "
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exec "foo" $*
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Copyright (C)<29>2003-2004 Harold Levy.
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This code links to the GNU readline library, and as such is bound by the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 2 or (at your option) any later version.
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The GNU General Public License is often shipped with GNU software, and is
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generally kept in a file called COPYING or LICENSE. If you do not have a
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copy of the license, write to the Free Software Foundation, 59 Temple Place,
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Suite 330, Boston, MA 02111 USA.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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*******************************************************************************
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******************************************************************************/
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#include <dlfcn.h>
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#include <stdio.h>
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#include <strings.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <readline/readline.h>
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#include <readline/history.h>
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/* for dynamically connecting to the native fgets() */
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#if defined(RTLD_NEXT)
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#define REAL_LIBC RTLD_NEXT
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#else
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#define REAL_LIBC ((void *) -1L)
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#endif
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typedef char * ( * fgets_t ) ( char * s, int n, FILE * stream ) ;
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/* private data */
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/* -- writeable data is stored in the shared library's data segment
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-- every process that uses the shared library gets a private memory copy of
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its entire data segment
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-- static data in the shared library is not copied to the application
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-- only read-only (i.e. 'const') data is stored in the shared library's
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text segment
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*/
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static char ** my_fgets_names = NULL ;
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static int my_fgets_number_of_names = 0 ;
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static int my_fgets_debug_flag = 0 ;
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/* invoked with _fgets_reset_ */
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static void
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my_fgets_reset (
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void
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) {
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if ( my_fgets_names && (my_fgets_number_of_names > 0) ) {
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int i ;
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if ( my_fgets_debug_flag ) {
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printf ( "libfgets: removing command list\n" ) ;
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}
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for ( i = 0 ; i < my_fgets_number_of_names ; i ++ ) {
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if ( my_fgets_names[i] ) free ( my_fgets_names[i] ) ;
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}
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free ( my_fgets_names ) ;
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}
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my_fgets_names = NULL ;
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my_fgets_number_of_names = 0 ;
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}
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/* invoked with _fgets_dump_ */
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static void
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my_fgets_dump (
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void
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) {
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char * s ;
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printf ( "\n" ) ;
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s = getenv ( "FGETS_PROMPT" ) ;
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printf ( "FGETS_PROMPT = %s\n", s ? s : "" ) ;
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s = getenv ( "FGETS_COMMAND_FILE" ) ;
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printf ( "FGETS_COMMAND_FILE = %s\n", s ? s : "" ) ;
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printf ( "debug flag = %d\n", my_fgets_debug_flag ) ;
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printf ( "#commands = %d\n", my_fgets_number_of_names ) ;
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if ( my_fgets_debug_flag ) {
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if ( my_fgets_names && (my_fgets_number_of_names > 0) ) {
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int i ;
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for ( i = 0 ; i < my_fgets_number_of_names ; i ++ ) {
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printf ( "%s\n", my_fgets_names[i] ) ;
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}
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}
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}
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printf ( "\n" ) ;
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}
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/* invoked with _fgets_debug_ */
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static void
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my_fgets_debug_toggle (
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void
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) {
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my_fgets_debug_flag = my_fgets_debug_flag ? 0 : 1 ;
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if ( my_fgets_debug_flag ) {
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printf ( "libfgets: debug flag = %d\n", my_fgets_debug_flag ) ;
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}
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}
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/* read the command list if needed, return the i-th name */
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static char *
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my_fgets_lookup (
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int index
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) {
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if ( (! my_fgets_names) || (! my_fgets_number_of_names) ) {
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char * fname ;
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FILE * fp ;
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fgets_t _fgets ;
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int i ;
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char buf1[256], buf2[256] ;
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fname = getenv ( "FGETS_COMMAND_FILE" ) ;
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if ( ! fname ) {
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if ( my_fgets_debug_flag ) {
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printf ( "libfgets: empty or unset FGETS_COMMAND_FILE\n" ) ;
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}
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return NULL ;
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}
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fp = fopen ( fname, "r" ) ;
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if ( ! fp ) {
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if ( my_fgets_debug_flag ) {
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printf ( "libfgets: cannot open '%s' for reading\n", fname ) ;
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}
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return NULL ;
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}
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_fgets = (fgets_t) dlsym ( REAL_LIBC, "fgets" ) ;
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if ( ! _fgets ) {
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fprintf ( stderr,
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"libfgets: failed to dynamically link to native fgets()\n"
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) ;
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return NULL ;
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}
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for ( i = 0 ; _fgets(buf1,255,fp) ; i ++ ) ;
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if ( ! i ) { fclose(fp) ; return NULL ; }
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my_fgets_names = (char**) calloc ( i, sizeof(char*) ) ;
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rewind ( fp ) ;
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i = 0 ;
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while ( _fgets(buf1,255,fp) ) {
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buf1[255] = 0 ;
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if ( 1 == sscanf(buf1,"%s",buf2) ) {
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my_fgets_names[i] = strdup(buf2) ;
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i ++ ;
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}
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}
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fclose ( fp ) ;
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my_fgets_number_of_names = i ;
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if ( my_fgets_debug_flag ) {
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printf ( "libfgets: successfully read %d commands\n", i ) ;
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}
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}
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if ( index < my_fgets_number_of_names ) {
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return my_fgets_names[index] ;
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} else {
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return NULL ;
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}
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}
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/* generate a list of partial name matches for readline() */
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static char *
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my_fgets_generator (
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const char * text,
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int state
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)
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{
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static int list_index, len ;
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char * name ;
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if ( ! state ) {
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list_index = 0 ;
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len = strlen ( text ) ;
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}
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while ( ( name = my_fgets_lookup(list_index) ) ) {
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list_index ++ ;
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if ( ! strncmp ( name, text, len ) ) {
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return ( strdup ( name ) ) ;
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}
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}
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return ( NULL ) ;
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}
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/* partial name completion callback for readline() */
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static char **
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my_fgets_completion (
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const char * text,
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int start,
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int end
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)
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{
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char ** matches ;
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matches = NULL ;
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if ( ! start ) {
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matches = rl_completion_matches ( text, my_fgets_generator ) ;
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}
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return ( matches ) ;
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}
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/* fgets() intercept */
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char *
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fgets (
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char * s,
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int n,
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FILE * stream
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)
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{
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if ( ! s ) return NULL ;
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if ( stream == stdin ) {
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char * prompt ;
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char * my_fgets_line ;
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rl_already_prompted = 1 ;
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rl_attempted_completion_function = my_fgets_completion ;
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rl_catch_signals = 1 ;
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rl_catch_sigwinch = 1 ;
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rl_set_signals () ;
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prompt = getenv ( "FGETS_PROMPT" ) ;
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for (
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my_fgets_line = 0 ; ! my_fgets_line ; my_fgets_line=readline(prompt)
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) ;
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if ( ! strncmp(my_fgets_line, "_fgets_reset_", 13) ) {
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my_fgets_reset () ;
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free ( my_fgets_line ) ;
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strcpy ( s, "\n" ) ;
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return ( s ) ;
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}
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if ( ! strncmp(my_fgets_line, "_fgets_dump_", 12) ) {
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my_fgets_dump () ;
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free ( my_fgets_line ) ;
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strcpy ( s, "\n" ) ;
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return ( s ) ;
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}
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if ( ! strncmp(my_fgets_line, "_fgets_debug_", 13) ) {
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my_fgets_debug_toggle () ;
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free ( my_fgets_line ) ;
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strcpy ( s, "\n" ) ;
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return ( s ) ;
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}
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(void) strncpy ( s, my_fgets_line, n-1 ) ;
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(void) strcat ( s, "\n" ) ;
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if ( *my_fgets_line ) add_history ( my_fgets_line ) ;
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free ( my_fgets_line ) ;
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return ( s ) ;
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} else {
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static fgets_t _fgets ;
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_fgets = (fgets_t) dlsym ( REAL_LIBC, "fgets" ) ;
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if ( ! _fgets ) {
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fprintf ( stderr,
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"libfgets: failed to dynamically link to native fgets()\n"
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) ;
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strcpy ( s, "\n" ) ;
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return ( s ) ;
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}
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return (
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_fgets ( s, n, stream )
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) ;
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}
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}
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