Source Code 1992 March/Source_Code_CD-ROM_Walnut_Creek_March_1992.iso/usenet/altsrcs/3/3970

Text File | 1991-09-05 | 7.5 KB | 253 lines

Path: wupost!uunet!mcsun!news.funet.fi!hydra!klaava!wirzeniu
From: [e-mail] (Lars Wirzenius)
Newsgroups: alt.sources
Subject: Unix-like CDPATH for MS-DOS
Keywords: Unix-like CD CDPATH MS-DOS
Message-ID: <[e-mail]>
Date: 4 Sep 91 14:43:01 GMT
Followup-To: alt.sources.d
Organization: University of Helsinki
Lines: 241

An extract from the README:

This shar file contains two source files for as many programs: lacd.c
and pwd.c.

The lacd program emulates the CDPATH-feature of several Unix shells
(i.e. the cd command prepends in turn each of the directories in the
CDPATH environment variable and tries to go to the resulting directory;
it stops as soon as it succeeds, of course). Read the beginning of the
source file for a manual of sorts.

(...)

Bug reports, critique, suggestions for improvement and other feed back
to [e-mail].

Lars Wirzenius


#!/bin/sh
#
#  This is a shar file.  To use:
#  1. Remove everything before the /bin/sh line
#  2. Execute with /bin/sh (not csh) to extract the files:
#         README
#         lacd.c
#         pwd.c
#
file="${0}"
echo extracting README 1>&2
sed 's/^X//' >README << 'EnD of README'
XThis shar file contains two source files for as many programs: lacd.c
Xand pwd.c.
X
XThe lacd program emulates the CDPATH-feature of several Unix shells
X(i.e. the cd command prepends in turn each of the directories in the
XCDPATH environment variable and tries to go to the resulting directory;
Xit stops as soon as it succeeds, of course). Read the beginning of the
Xsource file for a manual of sorts.
X
XYou may be familiar with 'directory jumping' programs like NCD (Norton
XCD, from the Norton Utilities), which build an auxiliary file with the
Xcomplete directory tree. These have the drawback that the auxiliary
Xfile needs to be updated (for many programs this means rebuilding) each
Xtime the directory tree changes, which can be awkward if you often
Xcreate directories from within several different programs, e.g.
XPC-Tools, Windows and installation programs; it can also be slow.
X
XIf you use CED, 4DOS or something similar, you may want to create an
Xalias cd that runs lacd instead the builtin command; that way you don't
Xneed to learn any new keyboard reflexes. Except that you do: you can't
Xjust use cd without arguments to get the current work directory (if
Xyou're like me and don't use $p in your PROMPT). The pwd program is
Xintended to remedy that: it prints the current work directory to the
Xstandard output.
X
XBug reports, critique, suggestions for improvement and other feed back
Xto [e-mail].
X
XLars Wirzenius
EnD of README
echo extracting lacd.c 1>&2
sed 's/^X//' >lacd.c << 'EnD of lacd.c'
X/*
X * Name:    lacd.c
X * Purpose:    Emulate the Unix cd command.
X * Description:    If there are no arguments, go to the 'home' directory
X *        (HOME or the root dir).
X *        Otherwise, if the argument begins with a backslash or
X *        dot or contains a drive, go to that directory.
X *        Otherwise, go to first directory that can be found by
X *        prepending a directory from CDPATH to the argument.
X *        Otherwise, print an error message.
X * Note:    HOME and CDPATH are environment variables. CDPATH consists
X *        of directories that are separated by semicolons (';').
X * Author:    Lars Wirzenius
X * Version:    1.01
X * Released:    1991-9-3 (aka September 3, 1991)
X */
X
X#include <stdio.h>
X#include <stdarg.h>
X#include <string.h>
X#include <stdlib.h>
X#include <errno.h>
X#include <ctype.h>
X#include <dir.h>
X
Xchar cwd[MAXPATH];        /* Original work dir, restored on error.
X                   This is a global variable, so it isn't
X                   necessary to have _everyone_ know
X                   about it. Now only main and error do. */
X
Xint try(char *target);
Xchar *egetenv(const char *env, const char *def);
Xchar *cat_names(const char *prefix, const char *suffix);
Xvoid error(const char *fmt, ...);
X
Xint main(int argc, char **argv) {
X    char *p, *q, *cdpath, *home, *arg, *buf;
X    int ok;
X
X    /* Save current work directory */
X    if (getcwd(cwd, sizeof(cwd)) == NULL) {
X        cwd[0] = '\0';        /* error needs _something_ in cwd */
X        error("Can't find the name of the current directory!\n");
X    }
X
X    arg = (argc == 1 || argv[1][0] == '\0') ? NULL : argv[1];
X    cdpath = egetenv("CDPATH", NULL);
X    home = egetenv("HOME", "\\");
X
X    if (arg == NULL)
X        ok = try(home);
X    else if (arg[0] == '\\' || arg[1] == ':' || arg[0] == '.'
X                 || cdpath == NULL)
X        ok = try(arg);
X    else {
X        /* Can't use strtok to separate parts of CDPATH, since
X           strtok won't return empty string for ";;". */
X        q = cdpath;
X        do {
X            p = q;
X            if ((q = strchr(q, ';')) != NULL) {
X                *q = '\0';    /* ok to modify, it's a copy,
X                           not the original */
X                ++q;
X            }
X            buf = cat_names(p, arg);
X            ok = try(buf);
X            if (ok && strcmp(p, ".") != 0 && *p != '\0')
X                printf("%s\n", buf);
X        } while (!ok && q != NULL);
X    }
X
X    if (!ok)
X        error("I'm lost, can't find anywhere to go\n");
X    if (fflush(stdout) != 0 || ferror(stdout))
X        error("Output error\n");
X
X    free(cdpath);
X    free(home);
X
X    exit(EXIT_SUCCESS);
X}
X
X
X/* Try to go to directory given as argument, return 0 for failure, nonzero
X   for success. */
Xint try(char *p) {
X    if (p[0] != '\0' && p[1] == ':')
X        setdisk(toupper(*p) - 'A');    /* no error return */
X    return chdir(p) == 0;
X}
X
X
X/* If the environment variable env exists, make copy of it, else make copy
X   of def. Abort program if copying fails, else return pointer to copy. */
Xchar *egetenv(const char *env, const char *def) {
X    const char *p;
X
X    if ((p = getenv(env)) == NULL)
X        p = def;
X    if (p != NULL && (p = strdup(p)) == NULL)
X        error("Out of memory?\n");
X    return (char *) p;    /* p is NULL or points to memory from
X                   strdup, so conversion is OK */
X}
X
X
X
X/* Concatenate prefix and suffix into a complete directory name into
X   static buffer, which may move (i.e., a previous return value may no
X   longer be valid after a new call) and is overwritten at each call */
Xchar *cat_names(const char *prefix, const char *suffix) {
X    static char *buf = NULL;
X    static size_t size = 0;
X    const char *sep;
X    const char *p;
X    size_t newsize;
X
X    if ((p = strchr(prefix, '\0')) > prefix)
X        --p;
X    sep = (*p == '\\' || *p == '\0') ? "" : "\\";
X    newsize = strlen(prefix) + strlen(sep) + strlen(suffix) + 1;
X    if (newsize > size) {
X        if ((buf = (char *) realloc(buf, newsize)) == NULL)
X            error("Out of memory? Can't continue, sorry.\n");
X        size = newsize;
X    }
X    sprintf(buf, "%s%s%s", prefix, sep, suffix);
X    return buf;
X}
X
X
X/* Print error message, try to restore cwd, and commit suicide. */
Xvoid error(const char *fmt, ...) {
X    va_list args;
X
X    if (errno != 0)
X        perror("lacd");
X    va_start(args, fmt);
X    (void) vfprintf(stderr, fmt, args);
X        /* If it doesn't work, then it doesn't work and there's
X           nothing we can do about it, so we'll ignore any error
X           code vfprintf may return. */
X    va_end(args);
X
X    if (cwd != '\0' && !try(cwd))
X        (void) fprintf(stderr, "Couldn't go back to %s!\n", cwd);
X
X    exit(EXIT_FAILURE);
X}
EnD of lacd.c
echo extracting pwd.c 1>&2
sed 's/^X//' >pwd.c << 'EnD of pwd.c'
X/*
X * Name:    pwd.c
X * Purpose:    Print the current working directory to stdout
X * Author:    Lars Wirzenius
X * Version:    1.00
X * Released:    1991-9-3 (aka September 3, 1991)
X */
X
X#include <stdio.h>
X#include <stdlib.h>
X#include <dir.h>
X
Xint main(void) {
X    char buf[MAXPATH];
X
X    if (getcwd(buf, sizeof(buf)) == NULL) {
X        perror("pwd: getcwd");
X        exit(EXIT_FAILURE);
X    }
X    puts(buf);
X    exit(EXIT_SUCCESS);
X}
EnD of pwd.c
--
Lars Wirzenius     [e-mail]