int posix_spawn_file_actions_addchdir(posix_spawn_file_actions_t *restrict, const char *restrict);

int posix_spawn_file_actions_addfchdir(posix_spawn_file_actions_t *, int);

a pathname that identifies the new process image file to execute.

a pathname that identifies the new process image file to execute; if the pathname does not start with a <slash> it shall be interpreted relative to the working directory of the child process after all file_actions have been performed.

the file parameter shall be used as the pathname for the new process image file.

the file parameter shall be used as the pathname for the new process image file; if this pathname does not start with a <slash> it shall be interpreted relative to the working directory of the child process after all file_actions have been performed.

The current working directory of the child process shall be the same as it is in the parent process.

The file actions specified by the spawn file actions object shall be performed in the order in which they were added to the spawn file actions object.

The file actions specified by the spawn file actions object shall be performed in the order in which they were added to the spawn file actions object, and relative file names in a given action shall be interpreted in relation to the tracked working directory. The tracked working directory shall begin with the current working directory of the parent process, and may be altered according to chdir or fchdir file actions; the current working directory of the child process shall be the final state of the tracked working directory after all file actions have been applied.

If the file_actions argument is not NULL, and specifies any close, dup2, or open actions to be performed, and if posix_spawn( ) or posix_spawnp( ) fails for any of the reasons that would cause close( ), dup2( ), or open( ) to fail, an error value shall be returned as described by close( ), dup2( ), and open( ), respectively

If the file_actions argument is not NULL, and specifies any chdir, close, dup2, fchdir, or open actions to be performed, and if posix_spawn( ) or posix_spawnp( ) fails for any of the reasons that would cause chdir( ), close( ), dup2( ), fchdir( ), or open( ) to fail, an error value shall be returned as described by chdir( ), close( ), dup2( ), fchdir( ), and open( ), respectively

control of six types of inheritance: file descriptors,

control of seven types of inheritance: file descriptors, current working directory,

Control of the current working directory is required because the parent process may want to constrain the resources that the child process can reach from its current working directory or affect how relative pathnames are interpreted, while recognizing that a multi-threaded parent process would require a lot of overhead to safely change its own working directory prior to creating the child process.

posix_spawn_file_actions_addchdir( ),

posix_spawn_file_actions_addchdir( )
NAME
posix_spawn_file_actions_addchdir, posix_spawn_file_actions_addfchdir - add chdir or fchdir action to spawn file actions object (ADVANCED REALTIME)
SYNOPSIS
<SPN>#include <spawn.h>
int posix_spawn_file_actions_addchdir(posix_spawn_file_actions_t *restrict file_actions, const char *restrict path);
int posix_spawn_file_actions_addfchdir(posix_spawn_file_actions_t *file_actions, int filedes);</SPN>
DESCRIPTION
The posix_spawn_file_actions_addchdir( ) function shall add a chdir action to the object referenced by file_actions that shall cause the working directory to be set to path (as if chdir(path) had been called) when a new process is spawned using this file actions object. A relative path shall be interpreted in relation to the working directory determined by any prior actions. The string described by path shall be copied by the posix_spawn_file_actions_addchdir( ) function.
The posix_spawn_file_actions_addfchdir( ) function shall add a fchdir action to the object referenced by file_actions that shall cause the working directory to be set to filedes (as if fchdir(filedes) had been called) when a new process is spawned using this file actions object.
A spawn file actions object is as defined in posix_spawn_file_actions_addclose( ).
RETURN VALUE
Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error.
ERRORS
The posix_spawn_file_actions_addfchdir( ) function shall fail if:
[EBADF] The value specified by fildes is negative.
These functions shall fail if:
[ENOMEM] Insufficient memory exists to add to the spawn file actions object.
It shall not be considered an error for the path or fildes argument passed to these functions to specify a path or file descriptor for which the specified operation could not be performed at the time of the call. Any such error will be detected when the associated file actions object is later used during a posix_spawn( ) or posix_spawnp( ) operation.
These functions may fail if:
[EINVAL] The value specified by file_actions is invalid.
EXAMPLES
None.
APPLICATION USAGE
The posix_spawn_file_actions_addchdir( ) and posix_spawn_file_actions_addfchdir( ) functions are part of the Spawn option and need not be provided on all implementations.
Changing the working directory of a child process can be useful when invoking utilities such as pax. Furthermore, the ability to add fchdir actions to posix_spawn( ) gives the caller as much control over relative pathnames processed in the context of the child as it would otherwise have using openat( ), since all file actions are processed in sequence in the context of the child at a point where the child process is still single-threaded. Without chdir or fchdir actions, changing the working directory of the child would require a shim utility (some implementations provide

env -C /new/path program args...

as an extension, but the standard does not require this extension), or else temporarily changing the working directory in the parent process prior to calling posix_spawn( ) (but this requires locking in a multi-threaded process, to ensure that no other thread is impacted by the temporary change to global state).
File actions are performed in a new process created by posix_spawn( ) or posix_spawnp( ) in the same order that they were added to the file actions object. Thus, the execution of an addopen action that was created by a call to posix_spawn_file_actions_addopen( ) that specifies a relative path will be affected by the execution of a chdir or fchdir action that was created by a previous call to posix_spawn_file_actions_addchdir( ) or posix_spawn_file_actions_addfchdir( ). Likewise, a relative path passed to posix_spawn( ) will be affected by the last chdir or fchdir action in the file action list.
RATIONALE
Refer to the RATIONALE section in posix_spawn_file_actions_addclose( ).
FUTURE DIRECTIONS
None.
SEE ALSO
chdir( ), fchdir( ), posix_spawn( ), posix_spawn_file_actions_addclose( ), posix_spawn_file_actions_destroy( ).
XBD <spawn.h>
CHANGE HISTORY
First released in Issue 8. Derived from Solaris posix_spawn_file_actions_addchdir_np.

or delete

A relative path shall be interpreted in relation to the working directory determined by any prior actions.

These functions shall fail if:
[ENOMEM] Insufficient memory exists to add to the spawn file actions object.

[ENOMEM] Insufficient memory exists to add to the spawn file actions object.

A spawn file actions object may be initialized to contain an ordered sequence of close( ), dup2( ), and open( ) operations to be used by posix_spawn( ) or posix_spawnp( ) to arrive at the set of open file descriptors inherited by the spawned process from the set of open file descriptors in the parent at the time of the posix_spawn( ) or posix_spawnp( ) call.

A spawn file actions object may be initialized to contain an ordered sequence of chdir( ), close( ), dup2( ), fchdir( ), and open( ) operations to be used by posix_spawn( ) or posix_spawnp( ) to arrive at the set of open file descriptors and current working directory inherited by the spawned process from the set of open file descriptors and current working directory in the parent at the time of the posix_spawn( ) or posix_spawnp( ) call.

posix_spawn_file_actions_addchdir( ),

posix_spawn_file_actions_addfchdir( )
NAME
posix_spawn_file_actions_addfchdir — add fchdir action to spawn file actions object (ADVANCED REALTIME)
SYNOPSIS
<SPN>#include <spawn.h>
int posix_spawn_file_actions_addfchdir(posix_spawn_file_actions_t
* file_actions, int fildes);</SPN>
DESCRIPTION
Refer to posix_spawn_file_actions_addchdir( ).

int posix_spawn_file_actions_addchdir(
  posix_spawn_file_actions_t *restrict file_actions,
  const char *restrict path);

int posix_spawn_file_actions_addfchdir(
   posix_spawn_file_actions_t *file_actions, int filedes);

else if (strncmp(p, "chdir(", 6) == 0)
{
    char path[1000]; /* Should be dynamic */
    char *q;

    p += 6
    q = strchr(p, '*');
    if (q == NULL)
        _exit(127);
    strncpy(path, p, q - p);
    path[q - p] = '\0';
    if (chdir(path) == -1)
        _exit(127);
}
else if (strncmp(p, "fchdir(", 7) == 0)
{
    int fd;

    if (sscanf(p + 7, "%d)", &fd) != 1)
        _exit(127);
    if (fchdir(fd) == -1)
        _exit(127);
}

/* Add a chdir action to object. */
int posix_spawn_file_actions_addchdir(
    posix_spawn_file_actions_t *restrict file_actions,
    const char *restrict path)
{
    char temp[100];

    sprintf(temp, "chdir(%s*)", path);
    return add_to_file_actions(file_actions, temp);
}
/* Add a fchdir action to object. */
int posix_spawn_file_actions_addfchdir(
    posix_spawn_file_actions_t *file_actions, int filedes)
{
    char temp[100];

    sprintf(temp, "fchdir(%d)", filedes);
    return add_to_file_actions(file_actions, temp);
}