lib/libbb.c

   1 /* vi: set sw=8 ts=8: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) many different people.
   6  * If you wrote this, please acknowledge your work.
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   9  */
  10
  11 #include <common.h>
  12 #include <libbb.h>
  13 #include <linux/stat.h>
  14 #include <fs.h>
  15 #include <xfuncs.h>
  16 #include <malloc.h>
  17 #include <environment.h>
  18
  19 /* concatenate path and file name to new allocation buffer,
  20  * not adding '/' if path name already has '/'
  21 */
  22 char *concat_path_file(const char *path, const char *filename)
  23 {
  24         char *lc, *str;
  25
  26         if (!path)
  27                 path = "";
  28         lc = last_char_is(path, '/');
  29         while (*filename == '/')
  30                 filename++;
  31
  32         str = xmalloc(strlen(path) + (lc==0 ? 1 : 0) + strlen(filename) + 1);
  33         sprintf(str, "%s%s%s", path, (lc==NULL ? "/" : ""), filename);
  34
  35         return str;
  36 }
  37 EXPORT_SYMBOL(concat_path_file);
  38
  39 /*
  40  * This function make special for recursive actions with usage
  41  * concat_path_file(path, filename)
  42  * and skipping "." and ".." directory entries
  43  */
  44
  45 char *concat_subpath_file(const char *path, const char *f)
  46 {
  47         if (f && DOT_OR_DOTDOT(f))
  48                 return NULL;
  49         return concat_path_file(path, f);
  50 }
  51 EXPORT_SYMBOL(concat_subpath_file);
  52
  53 /* check if path points to an executable file;
  54  * return 1 if found;
  55  * return 0 otherwise;
  56  */
  57 int execable_file(const char *name)
  58 {
  59         struct stat s;
  60         return (!stat(name, &s) && S_ISREG(s.st_mode));
  61 }
  62 EXPORT_SYMBOL(execable_file);
  63
  64
  65 /* search $PATH for an executable file;
  66  * return allocated string containing full path if found;
  67  * return NULL otherwise;
  68  */
  69 char *find_execable(const char *filename)
  70 {
  71         char *path, *p, *n;
  72
  73         p = path = strdup(getenv("PATH"));
  74         while (p) {
  75                 n = strchr(p, ':');
  76                 if (n)
  77                         *n++ = '\0';
  78                 if (*p != '\0') { /* it's not a PATH="foo::bar" situation */
  79                         p = concat_path_file(p, filename);
  80                         if (execable_file(p)) {
  81                                 free(path);
  82                                 return p;
  83                         }
  84                         free(p);
  85                 }
  86                 p = n;
  87         }
  88         free(path);
  89         return NULL;
  90 }
  91 EXPORT_SYMBOL(find_execable);
  92
  93 /* Find out if the last character of a string matches the one given.
  94  * Don't underrun the buffer if the string length is 0.
  95  */
  96 char* last_char_is(const char *s, int c)
  97 {
  98         if (s && *s) {
  99                 size_t sz = strlen(s) - 1;
 100                 s += sz;
 101                 if ( (unsigned char)*s == c)
 102                         return (char*)s;
 103         }
 104         return NULL;
 105 }
 106 EXPORT_SYMBOL(last_char_is);
 107
 108 /* Like strncpy but make sure the resulting string is always 0 terminated. */
 109 char * safe_strncpy(char *dst, const char *src, size_t size)
 110 {
 111         if (!size) return dst;
 112         dst[--size] = '\0';
 113         return strncpy(dst, src, size);
 114 }
 115 EXPORT_SYMBOL(safe_strncpy);
 116