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libbb: modify find_executable() to not temporarily write to PATH

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This allows to simplify "which" applet code

function                                             old     new   delta
find_executable                                       93     111     +18
which_main                                           191     177     -14
builtin_source                                       316     294     -22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 18/-36)            Total: -18 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2024-10-08 04:03:17 +02:00
parent 8c4bccb83e
commit 49d9e06fba
4 changed files with 48 additions and 54 deletions
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56
libbb/executable.c
View file

@ -21,14 +21,11 @@ int FAST_FUNC file_is_executable(const char *name)
/* search (*PATHp) for an executable file;
* return allocated string containing full path if found;
* PATHp points to the component after the one where it was found
* (or NULL),
* (or NULL if found in last component),
* you may call find_executable again with this PATHp to continue
* (if it's not NULL).
* return NULL otherwise; (PATHp is undefined)
* in all cases (*PATHp) contents are temporarily modified
* but are restored on return (s/:/NUL/ and back).
* return NULL otherwise (PATHp is undefined)
*/
char* FAST_FUNC find_executable(const char *filename, char **PATHp)
char* FAST_FUNC find_executable(const char *name, const char **PATHp)
{
/* About empty components in $PATH:
* http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html
@ -38,38 +35,45 @@ char* FAST_FUNC find_executable(const char *filename, char **PATHp)
* initial colon preceding the rest of the list, or as a trailing colon
* following the rest of the list.
*/
char *p, *n;
char *p = (char*) *PATHp;
p = *PATHp;
while (p) {
int ex;
if (!p)
return NULL;
while (1) {
const char *end = strchrnul(p, ':');
int sz = end - p;
n = strchr(p, ':');
if (n) *n = '\0';
p = concat_path_file(
p[0] ? p : ".", /* handle "::" case */
filename
);
ex = file_is_executable(p);
if (n) *n++ = ':';
if (ex) {
*PATHp = n;
if (sz != 0) {
p = xasprintf("%.*s/%s", sz, p, name);
} else {
/* We have xxx::yyy in $PATH,
* it means "use current dir" */
p = xstrdup(name);
// A bit of discrepancy wrt the path used if file is found here.
// bash 5.2.15 "type" returns "./NAME".
// GNU which v2.21 returns "/CUR/DIR/NAME".
// With -a, both skip over all colons: xxx::::yyy is the same as xxx::yyy,
// current dir is not tried the second time.
}
if (file_is_executable(p)) {
*PATHp = (*end ? end+1 : NULL);
return p;
}
free(p);
p = n;
} /* on loop exit p == NULL */
return p;
if (*end == '\0')
return NULL;
p = (char *) end + 1;
}
}
/* search $PATH for an executable file;
* return 1 if found;
* return 0 otherwise;
*/
int FAST_FUNC executable_exists(const char *filename)
int FAST_FUNC executable_exists(const char *name)
{
char *path = getenv("PATH");
char *ret = find_executable(filename, &path);
const char *path = getenv("PATH");
char *ret = find_executable(name, &path);
free(ret);
return ret != NULL;
}