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/* Copyright 1999-2009 Gentoo Foundation
* Distributed under the terms of the GNU General Public License v2
*/
#include <dirent.h>
#include <limits.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#define ENVD_CONFIG "/etc/env.d/python/config"
/* 127 is the standard return code for "command not found" */
#define EXIT_ERROR 127
char* dir_cat(const char* dir, const char* file)
{
size_t dir_len = strlen(dir);
char* abs = malloc(dir_len + strlen(file) + 2);
strcpy(abs, dir);
abs[dir_len] = '/';
abs[dir_len + 1] = 0;
return strcat(abs, file);
}
const char* find_path(const char* exe)
{
const char* last_slash = strrchr(exe, '/');
if (last_slash)
{
return strndup(exe, last_slash - exe);
}
char* path = strdup(getenv("PATH"));
char* state;
const char* token = strtok_r(path, ":", &state);
while (token)
{
/* If an element of PATH is empty ("::"), then it is "." */
if (! *token)
{
token = ".";
}
/* If it starts with "~/", use "${HOME}/" instead */
if (strncmp(token, "~/", 2) == 0)
{
char* home = getenv("HOME");
char* new_token = malloc(strlen(token) + strlen(home));
strcpy(new_token, home);
strcat(new_token, token + 1);
token = new_token;
}
struct stat sbuf;
char* str = dir_cat(token, exe);
if (stat(str, &sbuf) == 0 && (S_ISREG(sbuf.st_mode) || S_ISLNK(sbuf.st_mode)))
{
return token;
}
token = strtok_r(NULL, ":", &state);
}
return NULL;
}
/* True if a valid file name, and not "python" */
int valid_interpreter(const char* name)
{
if (! name || ! *name || (strcmp(name, "python") == 0))
{
return 0;
}
return 1;
}
int get_version(const char* name)
{
/* Only find files beginning with "python" - this is a fallback,
* so we only want CPython
*/
if (! valid_interpreter(name) || strncmp(name, "python", 6) != 0)
return -1;
int pos = 6;
int major = 0;
int minor = 0;
if (name[pos] < '0' || name[pos] > '9')
return -1;
do
{
major = major * 10 + name[pos] - '0';
if (! name[++pos])
return -1;
}
while (name[pos] >= '0' && name[pos] <= '9');
if (name[pos++] != '.')
return -1;
if (name[pos] < '0' || name[pos] > '9')
return -1;
do
{
minor = minor * 10 + name[pos] - '0';
if (! name[++pos])
return (major << 8) | minor;
}
while (name[pos] >= '0' && name[pos] <= '9');
return -1;
}
int filter_python(const struct dirent* file)
{
return get_version(file->d_name) != -1;
}
/* This implements a version sort, such that the following order applies:
* <invalid file names> (should never be seen)
* python2.6
* python2.9
* python2.10
* python3.0
* python3.1
* python3.2
* python9.1
* python9.9
* python9.10
* python10.1
* python10.9
* python10.10
*/
int sort_python(const struct dirent**f1, const struct dirent** f2)
{
int ver1 = get_version((*f1)->d_name);
int ver2 = get_version((*f2)->d_name);
return ver1 - ver2;
}
const char* find_latest(const char* exe)
{
int major = -1;
int minor = -1;
const char* path = find_path(exe);
if (! path || ! *path)
{
path = "/usr/bin";
}
struct dirent** namelist;
int n = scandir(path, &namelist, filter_python, sort_python);
const char* ret = NULL;
if (n < 0)
{
return NULL;
}
/* walk backwards through the list */
while (n--)
{
if (! ret)
ret = strdup(namelist[n]->d_name);
free(namelist[n]);
}
free(namelist);
return ret;
}
int main(int argc, char** argv)
{
const char* EPYTHON = getenv("EPYTHON");
if (! valid_interpreter(EPYTHON))
{
FILE* f = fopen(ENVD_CONFIG, "r");
if (f)
{
struct stat st;
fstat(fileno(f), &st);
size_t size = st.st_size;
char* cont = malloc(size + 1);
fgets(cont, size + 1, f);
fclose(f);
size_t len = strlen(cont);
if (len && cont[len - 1] == '\n')
cont[len - 1] = 0;
EPYTHON = cont;
}
}
if (! valid_interpreter(EPYTHON))
EPYTHON = find_latest(argv[0]);
if (! EPYTHON)
return EXIT_ERROR;
if (strchr(EPYTHON, '/'))
{
execv(EPYTHON, argv);
return EXIT_ERROR;
}
const char* path = find_path(argv[0]);
if (*path)
{
execv(dir_cat(path, EPYTHON), argv);
return EXIT_ERROR;
}
execvp(EPYTHON, argv);
return EXIT_ERROR;
}
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