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#include <string.h>
#include <stdio.h>
#include <stdlib.h>
/*
* Returns the analog of "cd path" from a directory "cwd".
* The root is defined as empty path (instead of "/")
* An attempt to go past the root (with "..") leaves the path at root.
* The cwd is not expanded.
*/
char *pathexpand(const char *cwd, const char *path)
{
static const char SEP[] = "/";
if (!*path) /* empty path -> "." (don't move) */
path = ".";
if (!*cwd || *SEP == *path) /* no cwd, or path begins with "/" */
cwd = "";
while (*cwd && *SEP == *cwd)
++cwd;
size_t len = strlen(cwd);
char *out = malloc(len + 1 + strlen(path) + 1);
char *p = strcpy(out, cwd) + len;
for (; *path; ++path)
{
char *pl;
if (p > out && p[-1] != *SEP)
*p++ = *SEP;
pl = p;
while (*path && *SEP != *path)
*p++ = *path++;
*p = '\0';
/* ..."//"... */
if (p == pl)
; /* just ignore */
/* ..."/./"... */
else if ( p - pl == 1 && '.' == *pl )
--p; /* just ignore */
/* ..."/../"... */
else if ( p - pl == 2 && '.' == pl[0] && '.' == pl[1] )
{
/* drop the last element of the resulting path */
if (pl > out && --pl > out)
for (--pl; pl > out && *SEP != *pl; --pl)
;
p = pl > out ? ++pl: out;
}
/* ..."/path/"... */
else if (*path)
*p++ = *path; /* just add the separator */
if (!*path)
break;
}
if (p > out+1 && *SEP == p[-1])
--p;
*p = '\0';
return out;
}
#ifdef CHECK_PATHEXPAND
static void check(const char *cwd, const char *path, const char *good)
{
static int n = 0;
printf("%-2d: %10s$ cd %s", ++n, cwd, path);
char *t = pathexpand(cwd, path);
if ( strcmp(t, good) )
printf(" ____________________failed(%s)\n", t);
else
printf(" \033[32m%s\033[0m\n", t);
free(t);
}
int main(int argc, char **argv)
{
/* 1 */ check("/onelevel", "aa", "onelevel/aa");
/* 2 */ check("/", "..", "");
/* 3 */ check("/", "../..", "");
/* 4 */ check("/one", "aa/../bb", "one/bb");
/* 5 */ check("/one/two", "aa//bb", "one/two/aa/bb");
/* 6 */ check("", "/aa//bb", "aa/bb");
/* 7 */ check("/one/two", "", "one/two");
/* 8 */ check("/one/two", "aa/..bb/x/../cc/", "one/two/aa/..bb/cc");
/* 9 */ check("/one/two", "aa/x/././cc////", "one/two/aa/x/cc");
/* 10 */ check("/one/two", "../../../../aa", "aa");
/* 11 */ check("one/", "../one/two", "one/two");
/* 12 */ check("", "../../two", "two");
/* 13 */ check("a/b/c", "../../two", "a/two");
/* 14 */ check("a/b/", "../two", "a/two");
/* 15 */ check("///", "../two", "two");
return 0;
}
#endif
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