Get the effective group id of the current process
Int_Type getegid ()
The getegid function returns the effective group ID of the
current process.
This function is not supported by all systems.
Get the effective user-id of the current process
Int_Type geteuid ()
The geteuid function returns the effective user-id of the
current process.
This function is not supported by all systems.
Get the group id of the current process
Integer_Type getgid ()
The getgid function returns the real group id of the current
process.
This function is not supported by all systems.
Get the current process id
Integer_Type getpid ()
The getpid function returns the current process identification
number.
Get the parent process id
Integer_Type getppid ()
The getpid function returns the process identification
number of the parent process.
This function is not supported by all systems.
Get a process's scheduling priority
result = getpriority (which, who)
The setpriority function may be used to obtain the kernel's
scheduling priority for a process, process group, or a user depending
upon the values of the which and who parameters.
Specifically, if the value of which is PRIO_PROCESS,
then the value of who specifies the process id of the affected
process. If which is PRIO_PGRP, then who
specifies a process group id. If which is PRIO_USER,
then the value of who is interpreted as a user id. For the
latter two cases, where which refers to a set of processes,
the value returned corresponds to the highest priority of a process
in the set. A value of 0 may be used for who to denote the process
id, process group id, or real user ID of the current process.
Upon success, the function returns the specified priority value. If
an error occurs, the function will return NULL with errno set
accordingly.
Get the user-id of the current process
Int_Type getuid ()
The getuid function returns the user-id of the current
process.
This function is not supported by all systems.
Send a signal to a process
Integer_Type kill (Integer_Type pid, Integer_Type sig)
This function may be used to send a signal given by the integer sig
to the process specified by pid. The function returns zero upon
success or -1 upon failure setting errno accordingly.
The kill function may be used to determine whether or not
a specific process exists:
define process_exists (pid)
{
if (-1 == kill (pid, 0))
return 0; % Process does not exist
return 1;
}
This function is not supported by all systems.
Create a named pipe
Int_Type mkfifo (String_Type name, Int_Type mode)
The mkfifo attempts to create a named pipe with the specified
name and mode (modified by the process's umask). The function
returns 0 upon success, or -1 and sets errno upon failure.
Not all systems support the mkfifo function and even on
systems that do implement the mkfifo system call, the
underlying file system may not support the concept of a named pipe,
e.g, an NFS filesystem.
Set the group-id of the current process
Int_Type setgid (Int_Type gid)
The setgid function sets the effective group-id of the current
process. It returns zero upon success, or -1 upon error and sets
errno appropriately.
This function is not supported by all systems.
Set the process group-id
Int_Type setpgid (Int_Type pid, Int_Type gid)
The setpgid function sets the group-id gid of the
process whose process-id is pid. If pid is 0, then the
current process-id will be used. If pgid is 0, then the pid
of the affected process will be used.
If successful 0 will be returned, otherwise the function will
return -1 and set errno accordingly.
This function is not supported by all systems.
Set the scheduling priority for a process
Int_Type setpriority (which, who, prio)
The setpriority function may be used to set the kernel's
scheduling priority for a process, process group, or a user depending
upon the values of the which and who parameters.
Specifically, if the value of which is PRIO_PROCESS, then the
value of who specifies the process id of the affected process.
If which is PRIO_PGRP, then who specifies a process
group id. If which is PRIO_USER, then the value of
who is interpreted as a user id. A value of 0 may be used for
who to denote the process id, process group id, or real user ID of
the current process.
Upon sucess, the setpriority function returns 0. If an error occurs,
-1 is returned and errno will be set accordingly.
The getpriority and setpriority functions may be used
to implement a nice function for incrementing the priority of
the current process as follows:
define nice (dp)
{
variable p = getpriority (PRIO_PROCESS, 0);
if (p == NULL)
return -1;
variable s = setpriority (PRIO_PROCESS, 0, p + dp);
if (s == -1)
return -1;
return getpriority (PRIO_PROCESS, 0);
}
Priority values are sometimes called "nice" values. The actual range of priority values is system dependent but commonly range from -20 to 20, with -20 being the highest scheduling priority, and +20 the lowest.
Set the user-id of the current process
Int_Type setuid (Int_Type id)
The setuid function sets the effective user-id of the current
process. It returns zero upon success, or -1 upon error and sets
errno appropriately.
This function is not supported by all systems.
Pause for a specified number of seconds
sleep (Double_Type n)
The sleep function delays the current process for the
specified number of seconds. If it is interrupted by a signal, it
will return prematurely.
Not all system support sleeping for a fractional part of a second.
Execute a shell command
Integer_Type system (String_Type cmd)
The system function may be used to execute the string
expression cmd in an inferior shell. This function is an
interface to the C system function which returns an
implementation-defined result. On Linux, it returns 127 if the
inferior shell could not be invoked, -1 if there was some other
error, otherwise it returns the return code for cmd.
define dir ()
{
() = system ("DIR");
}
system_intr, system_intr<@@ref>new_processnew_process, popen
Execute a shell command
Integer_Type system_intr (String_Type cmd)
The system_intr function performs the same task as the
system function, except that the SIGINT signal will not
be ignored by the calling process. This means that if a S-Lang script
calls system_intr function, and Ctrl-C is pressed, both the
command invoked by the system_intr function and the script
will be interrupted. In contrast, if the command were invoked using
the system function, only the command called by it would be
interrupted, but the script would continue executing.
Set the file creation mask
Int_Type umask (Int_Type m)
The umask function sets the file creation mask to the value of
m and returns the previous mask.
Get the system name
Struct_Type uname ()
The uname function returns a structure containing information
about the operating system. The structure contains the following
fields:
sysname (Name of the operating system)
nodename (Name of the node within the network)
release (Release level of the OS)
version (Current version of the release)
machine (Name of the hardware)
Not all systems support this function.