/*

Date: Tue, 16 Mar 2004 19:38:40 -0800

From: Harold Levy <Harold.Levy@synopsys.com>

Subject: fgets(stdin) --> readline() redirector

To: chet@po.cwru.edu

Hi Chet,

Here is something you may find useful enough to include in the readline

distribution. It is a shared library that redirects calls to fgets(stdin)

to readline() via LD_PRELOAD, and it supports a custom prompt and list of

command names. Many people have asked me for this file, so I thought I'd

pass it your way in hope of just including it with readline to begin with.

Best Regards,

-Harold

*/

/******************************************************************************

*******************************************************************************

FILE NAME: fgets.c TARGET: libfgets.so

AUTHOR: Harold Levy VERSION: 1.0

hlevy@synopsys.com

ABSTRACT: Customize fgets() behavior via LD_PRELOAD in the following ways:

-- If fgets(stdin) is called, redirect to GNU readline() to obtain

command-line editing, file-name completion, history, etc.

-- A list of commands for command-name completion can be configured by

setting the environment-variable FGETS_COMMAND_FILE to a file containing

the list of commands to be used.

-- Command-line editing with readline() works best when the prompt string

is known; you can set this with the FGETS_PROMPT environment variable.

-- There special strings that libfgets will interpret as internal commands:

_fgets_reset_ reset the command list

_fgets_dump_ dump status

_fgets_debug_ toggle debug messages

HOW TO BUILD: Here are examples of how to build libfgets.so on various

platforms; you will have to add -I and -L flags to configure access to

the readline header and library files.

(32-bit builds with gcc)

AIX: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldl -lreadline -ltermcap

HP-UX: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldld -lreadline

Linux: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldl -lreadline

SunOS: gcc -fPIC fgets.c -shared -o libfgets.so -lc -ldl -lgen -lreadline

(64-bit builds without gcc)

SunOS: SUNWspro/bin/cc -D_LARGEFILE64_SOURCE=1 -xtarget=ultra -xarch=v9 \

-KPIC fgets.c -Bdynamic -lc -ldl -lgen -ltermcap -lreadline

HOW TO USE: Different operating systems have different levels of support

for the LD_PRELOAD concept. The generic method for 32-bit platforms is to

put libtermcap.so, libfgets.so, and libreadline.so (with absolute paths)

in the LD_PRELOAD environment variable, and to put their parent directories

in the LD_LIBRARY_PATH environment variable. Unfortunately there is no

generic method for 64-bit platforms; e.g. for 64-bit SunOS, you would have

to build both 32-bit and 64-bit libfgets and libreadline libraries, and

use the LD_FLAGS_32 and LD_FLAGS_64 environment variables with preload and

library_path configurations (a mix of 32-bit and 64-bit calls are made under

64-bit SunOS).

EXAMPLE WRAPPER: Here is an example shell script wrapper around the

program "foo" that uses fgets() for command-line input:

#!/bin/csh

#### replace this with the libtermcap.so directory:

set dir1 = "/usr/lib"

#### replace this with the libfgets.so directory:

set dir2 = "/usr/fgets"

#### replace this with the libreadline.so directory:

set dir3 = "/usr/local/lib"

set lib1 = "${dir1}/libtermcap.so"

set lib2 = "${dir2}/libfgets.so"

set lib3 = "${dir3}/libreadline.so"

if ( "${?LD_PRELOAD}" ) then

setenv LD_PRELOAD "${lib1}:${lib2}:${lib3}:${LD_PRELOAD}"

else

setenv LD_PRELOAD "${lib1}:${lib2}:${lib3}"

endif

if ( "${?LD_LIBRARY_PATH}" ) then

setenv LD_LIBRARY_PATH "${dir1}:${dir2}:${dir3}:${LD_LIBRARY_PATH}"

else

setenv LD_LIBRARY_PATH "${dir1}:${dir2}:${dir3}"

endif

setenv FGETS_COMMAND_FILE "${dir2}/foo.commands"

setenv FGETS_PROMPT "foo> "

exec "foo" $*

Copyright (C)©2003-2004 Harold Levy.

This code links to the GNU readline library, and as such is bound by the

terms of the GNU General Public License as published by the Free Software

Foundation, either version 2 or (at your option) any later version.

The GNU General Public License is often shipped with GNU software, and is

generally kept in a file called COPYING or LICENSE. If you do not have a

copy of the license, write to the Free Software Foundation, 59 Temple Place,

Suite 330, Boston, MA 02111 USA.

This program is distributed in the hope that it will be useful, but WITHOUT

ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

FOR A PARTICULAR PURPOSE. See the GNU General Public License for more

details.

*******************************************************************************

******************************************************************************/



#include <dlfcn.h>

#include <stdio.h>

#include <strings.h>

#include <stdlib.h>

#include <unistd.h>

#include <readline/readline.h>

#include <readline/history.h>



/* for dynamically connecting to the native fgets() */

#if defined(RTLD_NEXT)

#define REAL_LIBC RTLD_NEXT

#else

#define REAL_LIBC ((void *) -1L)

#endif

typedef char * ( * fgets_t ) ( char * s, int n, FILE * stream ) ;



/* private data */

/* -- writeable data is stored in the shared library's data segment

-- every process that uses the shared library gets a private memory copy of

its entire data segment

-- static data in the shared library is not copied to the application

-- only read-only (i.e. 'const') data is stored in the shared library's

text segment

*/

static char ** my_fgets_names = NULL ;

static int my_fgets_number_of_names = 0 ;

static int my_fgets_debug_flag = 0 ;



/* invoked with _fgets_reset_ */

static void

my_fgets_reset (

void

) {

if ( my_fgets_names && (my_fgets_number_of_names > 0) ) {

int i ;

if ( my_fgets_debug_flag ) {

printf ( "libfgets: removing command list\n" ) ;

}

for ( i = 0 ; i < my_fgets_number_of_names ; i ++ ) {

if ( my_fgets_names[i] ) free ( my_fgets_names[i] ) ;

}

free ( my_fgets_names ) ;

}

my_fgets_names = NULL ;

my_fgets_number_of_names = 0 ;

}



/* invoked with _fgets_dump_ */

static void

my_fgets_dump (

void

) {

char * s ;

printf ( "\n" ) ;

s = getenv ( "FGETS_PROMPT" ) ;

printf ( "FGETS_PROMPT = %s\n", s ? s : "" ) ;

s = getenv ( "FGETS_COMMAND_FILE" ) ;

printf ( "FGETS_COMMAND_FILE = %s\n", s ? s : "" ) ;

printf ( "debug flag = %d\n", my_fgets_debug_flag ) ;

printf ( "#commands = %d\n", my_fgets_number_of_names ) ;

if ( my_fgets_debug_flag ) {

if ( my_fgets_names && (my_fgets_number_of_names > 0) ) {

int i ;

for ( i = 0 ; i < my_fgets_number_of_names ; i ++ ) {

printf ( "%s\n", my_fgets_names[i] ) ;

}

}

}

printf ( "\n" ) ;

}



/* invoked with _fgets_debug_ */

static void

my_fgets_debug_toggle (

void

) {

my_fgets_debug_flag = my_fgets_debug_flag ? 0 : 1 ;

if ( my_fgets_debug_flag ) {

printf ( "libfgets: debug flag = %d\n", my_fgets_debug_flag ) ;

}

}



/* read the command list if needed, return the i-th name */

static char *

my_fgets_lookup (

int index

) {

if ( (! my_fgets_names) || (! my_fgets_number_of_names) ) {

char * fname ;

FILE * fp ;

fgets_t _fgets ;

int i ;

char buf1[256], buf2[256] ;

fname = getenv ( "FGETS_COMMAND_FILE" ) ;

if ( ! fname ) {

if ( my_fgets_debug_flag ) {

printf ( "libfgets: empty or unset FGETS_COMMAND_FILE\n" ) ;

}

return NULL ;

}

fp = fopen ( fname, "r" ) ;

if ( ! fp ) {

if ( my_fgets_debug_flag ) {

printf ( "libfgets: cannot open '%s' for reading\n", fname ) ;

}

return NULL ;

}

_fgets = (fgets_t) dlsym ( REAL_LIBC, "fgets" ) ;

if ( ! _fgets ) {

fprintf ( stderr,

"libfgets: failed to dynamically link to native fgets()\n"

) ;

return NULL ;

}

for ( i = 0 ; _fgets(buf1,255,fp) ; i ++ ) ;

if ( ! i ) { fclose(fp) ; return NULL ; }

my_fgets_names = (char**) calloc ( i, sizeof(char*) ) ;

rewind ( fp ) ;

i = 0 ;

while ( _fgets(buf1,255,fp) ) {

buf1[255] = 0 ;

if ( 1 == sscanf(buf1,"%s",buf2) ) {

my_fgets_names[i] = strdup(buf2) ;

i ++ ;

}

}

fclose ( fp ) ;

my_fgets_number_of_names = i ;

if ( my_fgets_debug_flag ) {

printf ( "libfgets: successfully read %d commands\n", i ) ;

}

}

if ( index < my_fgets_number_of_names ) {

return my_fgets_names[index] ;

} else {

return NULL ;

}

}



/* generate a list of partial name matches for readline() */

static char *

my_fgets_generator (

const char * text,

int state

)

{

static int list_index, len ;

char * name ;

if ( ! state ) {

list_index = 0 ;

len = strlen ( text ) ;

}

while ( ( name = my_fgets_lookup(list_index) ) ) {

list_index ++ ;

if ( ! strncmp ( name, text, len ) ) {

return ( strdup ( name ) ) ;

}

}

return ( NULL ) ;

}



/* partial name completion callback for readline() */

static char **

my_fgets_completion (

)

{

char ** matches ;

matches = NULL ;

if ( ! start ) {

matches = rl_completion_matches ( text, my_fgets_generator ) ;

}

return ( matches ) ;

}



/* fgets() intercept */

char *

fgets (

)

{

if ( ! s ) return NULL ;

if ( stream == stdin ) {

char * prompt ;

char * my_fgets_line ;

rl_already_prompted = 1 ;

rl_attempted_completion_function = my_fgets_completion ;

rl_catch_signals = 1 ;

rl_catch_sigwinch = 1 ;

rl_set_signals () ;

prompt = getenv ( "FGETS_PROMPT" ) ;

for (

my_fgets_line = 0 ; ! my_fgets_line ; my_fgets_line=readline(prompt)

) ;

if ( ! strncmp(my_fgets_line, "_fgets_reset_", 13) ) {

my_fgets_reset () ;

free ( my_fgets_line ) ;

strcpy ( s, "\n" ) ;

return ( s ) ;

}

if ( ! strncmp(my_fgets_line, "_fgets_dump_", 12) ) {

my_fgets_dump () ;

free ( my_fgets_line ) ;

strcpy ( s, "\n" ) ;

return ( s ) ;

}

if ( ! strncmp(my_fgets_line, "_fgets_debug_", 13) ) {

my_fgets_debug_toggle () ;

free ( my_fgets_line ) ;

strcpy ( s, "\n" ) ;

return ( s ) ;

}

(void) strncpy ( s, my_fgets_line, n-1 ) ;

(void) strcat ( s, "\n" ) ;

if ( *my_fgets_line ) add_history ( my_fgets_line ) ;

free ( my_fgets_line ) ;

return ( s ) ;

} else {

static fgets_t _fgets ;

_fgets = (fgets_t) dlsym ( REAL_LIBC, "fgets" ) ;

if ( ! _fgets ) {

fprintf ( stderr,

"libfgets: failed to dynamically link to native fgets()\n"

) ;

strcpy ( s, "\n" ) ;

return ( s ) ;

}

return (

_fgets ( s, n, stream )

) ;

}

}