105 lines
2.2 KiB
C
105 lines
2.2 KiB
C
/* vi: set sw=4 ts=4: */
|
|
/*
|
|
* xreadlink.c - safe implementation of readlink.
|
|
* Returns a NULL on failure...
|
|
*/
|
|
|
|
#include "libbb.h"
|
|
|
|
/*
|
|
* NOTE: This function returns a malloced char* that you will have to free
|
|
* yourself. You have been warned.
|
|
*/
|
|
char *xmalloc_readlink(const char *path)
|
|
{
|
|
enum { GROWBY = 80 }; /* how large we will grow strings by */
|
|
|
|
char *buf = NULL;
|
|
int bufsize = 0, readsize = 0;
|
|
|
|
do {
|
|
bufsize += GROWBY;
|
|
buf = xrealloc(buf, bufsize);
|
|
readsize = readlink(path, buf, bufsize);
|
|
if (readsize == -1) {
|
|
free(buf);
|
|
return NULL;
|
|
}
|
|
} while (bufsize < readsize + 1);
|
|
|
|
buf[readsize] = '\0';
|
|
|
|
return buf;
|
|
}
|
|
|
|
/*
|
|
* this routine is not the same as realpath(), which canonicalizes
|
|
* the given path completely. this routine only follows trailing
|
|
* symlinks until a real file is reached, and returns its name.
|
|
* intermediate symlinks are not expanded. as above, a malloced
|
|
* char* is returned, which must be freed.
|
|
*/
|
|
char *xmalloc_readlink_follow(const char *path)
|
|
{
|
|
char *buf = NULL, *lpc, *linkpath;
|
|
int bufsize;
|
|
smallint looping = 0;
|
|
|
|
buf = strdup(path);
|
|
bufsize = strlen(path) + 1;
|
|
|
|
while(1) {
|
|
linkpath = xmalloc_readlink(buf);
|
|
if (!linkpath) {
|
|
if (errno == EINVAL) /* not a symlink */
|
|
return buf;
|
|
free(buf);
|
|
return NULL;
|
|
}
|
|
|
|
if (*linkpath == '/') {
|
|
free(buf);
|
|
buf = linkpath;
|
|
bufsize = strlen(linkpath) + 1;
|
|
} else {
|
|
bufsize += strlen(linkpath);
|
|
if (looping++ > MAXSYMLINKS) {
|
|
free(linkpath);
|
|
free(buf);
|
|
return NULL;
|
|
}
|
|
buf = xrealloc(buf, bufsize);
|
|
lpc = bb_get_last_path_component_strip(buf);
|
|
strcpy(lpc, linkpath);
|
|
free(linkpath);
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
char *xmalloc_readlink_or_warn(const char *path)
|
|
{
|
|
char *buf = xmalloc_readlink(path);
|
|
if (!buf) {
|
|
/* EINVAL => "file: Invalid argument" => puzzled user */
|
|
bb_error_msg("%s: cannot read link (not a symlink?)", path);
|
|
}
|
|
return buf;
|
|
}
|
|
|
|
/* UNUSED */
|
|
#if 0
|
|
char *xmalloc_realpath(const char *path)
|
|
{
|
|
#if defined(__GLIBC__) && !defined(__UCLIBC__)
|
|
/* glibc provides a non-standard extension */
|
|
return realpath(path, NULL);
|
|
#else
|
|
char buf[PATH_MAX+1];
|
|
|
|
/* on error returns NULL (xstrdup(NULL) ==NULL) */
|
|
return xstrdup(realpath(path, buf));
|
|
#endif
|
|
}
|
|
#endif
|