/**
* slibc — Yet another C library
* Copyright © 2015 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <unistd.h>
#include <stdarg.h>
#include <errno.h>
#include <alloca.h>
#include <string.h>
#include <stdlib.h>
/**
* The current environment variables.
*/
extern char** environ;
/**
* Common code for the `execl*` functions.
*
* @param file The first argument of said functions.
* @param argv The rest of the arguments of said functions;
* may conclude `envp`.
* @param fetch_envp Whether `argv` includes `envp`.
* @param use_path Whether $PATH may be used.
*
* @throws Any error specified for execve(2).
*/
static void vexec(const char* file, va_list argv, int fetch_envp, int use_path)
{
char* const* envp = environ;
size_t n = 0, i;
va_list args;
char** argv_;
va_copy(args, argv);
while (n++, va_arg(args, char*) != NULL)
break;
if (fetch_envp)
envp = va_arg(args, char* const*);
argv_ = alloca(n * sizeof(char*));
for (i = 0; i < n; i++)
argv_[i] = va_arg(args, char*);
(void)(use_path ? execvpe : execve)(file, argv_, envp);
}
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execl(const char* path, ... /*, NULL */)
{
int saved_errno;
va_list argv;
va_start(argv, path);
vexec(path, argv, 0, 0);
saved_errno = errno;
va_end(argv);
return errno = saved_errno, -1;
}
/**
* Replace the current process image with a new process image.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execlp(const char* file, ... /*, NULL */)
{
int saved_errno;
va_list argv;
va_start(argv, path);
vexec(path, argv, 0, 1);
saved_errno = errno;
va_end(argv);
return errno = saved_errno, -1;
}
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be foramtted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execle(const char* path, ... /*, NULL, char* const envp[] */)
{
int saved_errno;
va_list argv;
va_start(argv, path);
vexec(path, argv, 1, 0);
saved_errno = errno;
va_end(argv);
return errno = saved_errno, -1;
}
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension, added for completeness.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be foramtted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execlpe(const char* file, ... /*, NULL, char* const envp[] */)
{
int saved_errno;
va_list argv;
va_start(argv, path);
vexec(path, argv, 1, 1);
saved_errno = errno;
va_end(argv);
return errno = saved_errno, -1;
}
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execv(const char* path, char* const argv[])
{
return execve(path, argv, environ);
}
/**
* Replace the current process image with a new process image.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execvp(const char* file, char* const argv[])
{
return execvpe(path, argv, environ);
}
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be foramtted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execve(const char* path, char* const argv[], char* const envp[])
{
return errno = ENOTSUP, -1;
(void) path, (void) argv, (void) enpv;
/* TODO implement execve */
}
/**
* Replace the current process image with a new process image.
*
* This is a GNU-compliant slibc extension.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be foramtted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*/
int execvpe(const char* file, char* const argv[], char* const envp[])
{
char* path = NULL;
char* path_cwd = NULL;
char* path_def = NULL;
char* path_env;
char* pathname = NULL;
char* p;
char* q;
size_t len = 0;
int eacces = 0;
int saved_errno;
if (strchr(file, '/'))
return execve(file, argv, envp);
if (!*file)
return errno = ENOENT, -1;
path_env = getenv(PATH);
if (path_env == NULL)
{
path_cwd = get_current_dir_name();
if (path_cwd == NULL)
goto fail;
len = confstr(_CS_PATH, NULL, 0);
if (len)
{
path_def = malloc((1 + len) * sizeof(char));
if (path_def == NULL)
goto fail;
*path_def = ':';
if (confstr(_CS_PATH, path_def + 1, len))
path_def = NULL, len = 0;
}
if (path_def == NULL)
path_def = ":/usr/local/bin:/bin:/usr/bin";
path = malloc((strlen(path_cwd) + strlen(path_def) + 1) * sizeof(char));
if (path == NULL)
goto fail;
stpcpy(stpcpy(path, path_cwd), path_def);
free(path_cwd), path_cwd = NULL;
if (len)
free(path_def), path_def = NULL;
}
else
if (path = strdup(path_env), path == NULL)
goto fail;
pathname = malloc((strlen(path) + strlen(file) + 2) * sizeof(char));
for (p = path; *p; p = q + 1)
{
q = strchr(p, ':');
if (q == p)
continue;
*q = '\0';
stpcpy(stpcpy(stpcpy(pathname, p), "/"), file);
execve(pathname, argv, envp);
if (errno == EACCES)
eacces = 1;
else if (errno != ENOENT)
goto fail;
}
free(path);
free(pathname);
return errno = (eaccess ? EACCES : ENOENT), -1;
fail:
saved_errno = errno;
free(path_cwd);
if (len)
free(path_def);
free(path);
free(pathname);
errno = saved_errno;
return -1;
}
