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sortix--sortix/libc/execvpe.cpp
Jonas 'Sortie' Termansen 15c48f4efc Add PATH variable.
2013-12-17 14:30:29 +01:00

100 lines
3.3 KiB
C++

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library 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 Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
execvpe.cpp
Loads a process image.
*******************************************************************************/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
// TODO: Move this to some generic environment interface!
static const char* LookupEnvironment(const char* name, char* const* envp)
{
size_t equalpos = strcspn(name, "=");
if ( name[equalpos] == '=' )
return NULL;
size_t namelen = equalpos;
for ( size_t i = 0; envp[i]; i++ )
{
if ( strncmp(name, envp[i], namelen) )
continue;
if ( envp[i][namelen] != '=' )
continue;
return envp[i] + namelen + 1;
}
return NULL;
}
// TODO: Provide an interface that allows user-space to find out which command
// would have been executed (according to PATH) had execvpe been called now.
// This is of value to programs such as which(1), instead of repeating much of
// this logic there.
extern "C" int execvpe(const char* filename, char* const* argv,
char* const* envp)
{
const char* path = LookupEnvironment("PATH", envp);
// TODO: Should there be a default PATH value?
if ( strchr(filename, '/') || !path )
return execve(filename, argv, envp);
// Search each directory in the PATH variable for a suitable file.
size_t filename_len = strlen(filename);
while ( *path )
{
size_t len = strcspn(path, ":");
if ( !len )
{
// Sortix doesn't support that the empty string means current
// directory. While it does inductively make sense, the common
// kernel interfaces such as openat doesn't accept it and software
// often just prefix their directories and a colon to PATH without
// regard to whether it's already empty. S
path++;
continue;
}
// Determine the full path to the file if it is in the directory.
size_t fullpath_len = len + 1 + filename_len + 1;
char* fullpath = (char*) malloc(fullpath_len * sizeof(char));
if ( !fullpath )
return -1;
stpcpy(stpcpy(stpncpy(fullpath, path, len), "/"), filename);
if ( (path += len + 1)[0] == ':' )
path++;
execve(fullpath, argv, envp);
free(fullpath);
// TODO: There may be some security concerns here as to whether to
// continue or abort execution. For instance, if a directory in the
// start of the PATH has permissions set up too restrictively, then
// it would never look in the later directories (and you can't execute
// anything without absolute paths). And other situations.
if ( errno == EACCES )
return -1;
if ( errno == ENOENT )
continue;
}
return -1;
}