Module (chicken process-context posix)

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== Module (chicken process-context posix)

This module provides access to POSIX-specific procedures which deal
with the current process context.

=== Process filesystem context

==== change-directory*

<procedure>(change-directory* FD)</procedure>
<procedure>(set! (current-directory) FD)</procedure>

Changes the current working directory to the one represented by the
file-descriptor {{FD}}, which should be an exact integer.

'''NOTE''': Windows does not allow {{{open}}} on directories, so while
technically it is supported, in practice you cannot use this procedure
on native Windows builds (on cygwin it works because cygwin emulates
this).

==== set-root-directory!

<procedure>(set-root-directory! STRING)</procedure>

Sets the root directory for the current process to the path given in
{{STRING}} (using the {{chroot}} function).  If the current process
has no root permissions, the operation will fail.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.


=== Retrieving user & group information

==== current-user-id

<procedure>(current-user-id)</procedure>
 [setter] (set! (current-user-id) UID)

Get or set the real user-id of the current process. The procedure corresponds to the getuid and setuid C functions.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

==== current-user-name

<procedure>(current-user-name)</procedure>

Get the login name corresponding to the real user-id of the current
process from the system password database.

On Windows, there's no user-id and no distinction between real and
effective user, but this procedure ''will'' return the username
associated with the current process, so it is safe to use.


==== current-effective-user-id

<procedure>(current-effective-user-id)</procedure>
 [setter] (set! (current-effective-user-id) UID)

Get or set the effective user-id of the current process.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

==== current-effective-user-name

<procedure>(current-effective-user-name)</procedure>

Get the login name corresponding to the effective user-id of the
current process from the system password database.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

==== current-group-id

<procedure>(current-group-id)</procedure>
 [setter] (set! (current-group-id) GID)

Get or set the real group-id of the current process.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

==== current-effective-group-id

<procedure>(current-effective-group-id)</procedure>
 [setter] (set! (current-effective-group-id) GID)

Get or set the effective group-id of the current process.
ID can be found, then {{#f}} is returned.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.


=== Process identity

==== current-process-id

<procedure>(current-process-id)</procedure>

Returns the process ID of the current process.

==== parent-process-id

<procedure>(parent-process-id)</procedure>

Returns the process ID of the parent of the current process.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

==== process-group-id

<procedure>(process-group-id PID)</procedure>
 [setter] (set! (process-group-id PID) PGID)

Get or set the process group ID of the process specified by {{PID}}.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

==== user-information

<procedure>(user-information USER [AS-VECTOR])</procedure>

If {{USER}} specifes a valid username (as a string) or user ID, then
the user database is consulted and a list of 7 values are returned:
the user-name, the encrypted password, the user ID, the group ID, a
user-specific string, the home directory and the default shell. When
{{AS-VECTOR}} is {{#t}} a vector of 7 elements is returned instead of
a list. If no user with this name or id then {{#f}} is returned.

Note: on Android systems, the user-specific string is always {{""}},
since {{pw_gecos}} is not available in the C {{passwd}} struct on that
platform.

'''NOTE''': On native Windows builds (all except cygwin), this
procedure is unimplemented and will raise an error.

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