rle_open_f.c

Go to the documentation of this file.

/*
 * rle_open_f.c - Open a file with defaults.
 *
 * Author :     Jerry Winters
 *      EECS Dept.
 *      University of Michigan
 * Date:    11/14/89
 * Copyright (c) 1990, University of Michigan
 */

#include "rle_config.h"
#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE  /* Make sure fdopen() is in stdio.h */
#endif /* !_XOPEN_SOURCE */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

#ifndef NO_OPEN_PIPES
/* Need to have a SIGCLD signal catcher. */
#include <signal.h>
#include <sys/wait.h>
#include <errno.h>

/* Count outstanding children.  Assume no more than 100 possible. */
#define MAX_CHILDREN 100
static int catching_children = 0;
static int pids[MAX_CHILDREN];

static FILE *my_popen();
#endif /* !NO_OPEN_PIPES */


/*
 *  Purpose : Open a file for input or ouput as controlled by the mode
 *  parameter.  If no file name is specified (ie. file_name is null) then
 *  a pointer to stdin or stdout will be returned.  The calling routine may
 *  call this routine with a file name of "-".  For this case rle_open_f
 *  will return a pointer to stdin or stdout depending on the mode.
 *    If the user specifies a non-null file name and an I/O error occurs
 *  when trying to open the file, rle_open_f will terminate execution with
 *  an appropiate error message.
 *
 *  parameters
 *   input:
 *     prog_name:   name of the calling program.
 *     file_name :  name of the file to open
 *     mode :       either "r" for read or input file or "w" for write or
 *                  output file
 *
 *   output:
 *     a file pointer
 *
 */
FILE *
rle_open_f_noexit( prog_name, file_name, mode )
char *prog_name, *file_name, *mode;
{
    FILE *fp;
    void perror();
    CONST_DECL char *err_str;
    register char *cp;
    char *combuf;

#ifdef STDIO_NEEDS_BINARY
    char mode_string[32];   /* Should be enough. */

    /* Concatenate a 'b' onto the mode. */
    mode_string[0] = mode[0];
    mode_string[1] = 'b';
    strcpy( mode_string + 2, mode + 1 );
    mode = mode_string;
#endif

    if ( *mode == 'w' || *mode == 'a' )
    fp = stdout;     /* Set the default value */
    else
    fp = stdin;

    if ( file_name != NULL && strcmp( file_name, "-" ) != 0 )
    {
#ifndef NO_OPEN_PIPES
    /* Check for dead children. */
    if ( catching_children > 0 )
    {
        int i, j;

        /* Check all children to see if any are dead, reap them if so. */
        for ( i = 0; i < catching_children; i++ )
        {
        /* The assumption here is that if it's dead, the kill
         * will fail, but, because we haven't waited for
         * it yet, it's a zombie.
         */
        if (kill(pids[i], 0) < 0) {
            int opid = pids[i], pid = 0;
            /* Wait for processes & delete them from the list,
             * until we get the one we know is dead.
             * When removing one earlier in the list than
             * the one we found, decrement our loop index.
             */
            while (pid != opid) {
            pid = wait( NULL );
            for ( j = 0;
                  j < catching_children && pids[j] != pid;
                  j++ )
                ;
#ifdef DEBUG
            fprintf( stderr, "Reaping %d at %d for %d at %d\n",
                 pid, j, opid, i );
            fflush( stderr );
#endif
            if ( pid < 0 )
                break;
            if ( j < catching_children ) {
                if ( i >= j )
                i--;
                for ( j++; j < catching_children; j++ )
                pids[j-1] = pids[j];
                catching_children--;
            }
            }
        }
        }
    }

    /*  Real file, not stdin or stdout.  If name ends in ".Z",
     *  pipe from/to un/compress (depending on r/w mode).
     *
     *  If it starts with "|", popen that command.
     */

    cp = file_name + strlen( file_name ) - 2;
    /* Pipe case. */
    if ( *file_name == '|' )
    {
        int thepid;     /* PID from my_popen */
        if ( (fp = my_popen( file_name + 1, mode, &thepid )) == NULL )
        {
        err_str = "%s: can't invoke <<%s>> for %s: ";
        goto err;
        }
        /* One more child to catch, eventually. */
        if (catching_children < MAX_CHILDREN) {
#ifdef DEBUG
        fprintf( stderr, "Forking %d at %d\n",
             thepid, catching_children );
        fflush( stderr );
#endif
        pids[catching_children++] = thepid;
        }
    }

    /* Compress case. */
    else if ( cp > file_name && *cp == '.' && *(cp + 1) == 'Z' )
    {
        int thepid;     /* PID from my_popen. */
        combuf = (char *)malloc( 20 + strlen( file_name ) );
        if ( combuf == NULL )
        {
        err_str = "%s: out of memory opening (compressed) %s for %s";
        goto err;
        }

        if ( *mode == 'w' )
        sprintf( combuf, "compress > %s", file_name );
        else if ( *mode == 'a' )
        sprintf( combuf, "compress >> %s", file_name );
        else
        sprintf( combuf, "compress -d < %s", file_name );

        fp = my_popen( combuf, mode, &thepid );
        free( combuf );

        if ( fp == NULL )
        {
        err_str =
    "%s: can't invoke 'compress' program, trying to open %s for %s";
        goto err;
        }
        /* One more child to catch, eventually. */
        if (catching_children < MAX_CHILDREN) {
#ifdef DEBUG
        fprintf( stderr, "Forking %d at %d\n", thepid, catching_children );
        fflush( stderr );
#endif
        pids[catching_children++] = thepid;
        }
    }

    /* Ordinary, boring file case. */
    else
#endif /* !NO_OPEN_PIPES */
        if ( (fp = fopen(file_name, mode)) == NULL )
        {
        err_str = "%s: can't open %s for %s: ";
        goto err;
        }
    }

    return fp;

err:
    fprintf( stderr, err_str,
         prog_name, file_name,
         (*mode == 'w') ? "output" :
         (*mode == 'a') ? "append" :
         "input" );
    perror( "" );
    return NULL;

}

FILE *
rle_open_f( prog_name, file_name, mode )
char *prog_name, *file_name, *mode;
{
    FILE *fp;

    if ( (fp = rle_open_f_noexit( prog_name, file_name, mode )) == NULL )
    exit( -1 );

    return fp;
}


/*****************************************************************
 * TAG( rle_close_f )
 *
 * Close a file opened by rle_open_f.  If the file is stdin or stdout,
 * it will not be closed.
 * Inputs:
 *  fd: File to close.
 * Outputs:
 *  None.
 * Assumptions:
 *  fd is open.
 * Algorithm:
 *  If fd is NULL, just return.
 *  If fd is stdin or stdout, don't close it.  Otherwise, call fclose.
 */
void
rle_close_f( fd )
FILE *fd;
{
    if ( fd == NULL || fd == stdin || fd == stdout )
    return;
    else
    fclose( fd );
}


#ifndef NO_OPEN_PIPES
static FILE *
my_popen( cmd, mode, pid )
char *cmd, *mode;
int *pid;
{
    FILE *retfile;
    int thepid = 0;
    int pipefd[2];
    int i;
    char *argv[4];

    /* Check args. */
    if ( *mode != 'r' && *mode != 'w' )
    {
    errno = EINVAL;
    return NULL;
    }

    if ( pipe(pipefd) < 0 )
    return NULL;

    /* Flush known files. */
    fflush(stdout);
    fflush(stderr);
    if ( (thepid = fork()) < 0 )
    {
    close(pipefd[0]);
    close(pipefd[1]);
    return NULL;
    }
    else if (thepid == 0) {
    /* In child. */
    /* Rearrange file descriptors. */
    if ( *mode == 'r' )
    {
        /* Parent reads from pipe, so reset stdout. */
        close(1);
        dup2(pipefd[1],1);
    } else {
        /* Parent writing to pipe. */
        close(0);
        dup2(pipefd[0],0);
    }
    /* Close anything above fd 2. (64 is an arbitrary magic number). */
    for ( i = 3; i < 64; i++ )
        close(i);

    /* Finally, invoke the program. */
    if ( execl("/bin/sh", "sh", "-c", cmd, NULL) < 0 )
        exit(127);
    /* NOTREACHED */
    }

    /* Close file descriptors, and gen up a FILE ptr */
    if ( *mode == 'r' )
    {
    /* Parent reads from pipe. */
    close(pipefd[1]);
    retfile = fdopen( pipefd[0], mode );
    } else {
    /* Parent writing to pipe. */
    close(pipefd[0]);
    retfile = fdopen( pipefd[1], mode );
    }

    /* Return the PID. */
    *pid = thepid;

    return retfile;
}
#endif /* !NO_OPEN_PIPES */