f90_unix_env: Unix Environment Functions Module

Table of Contents

1 Name

f90_unix_env — Module of Unix environment functions

2 Usage

USE F90_UNIX_ENV

This module contains part of a Fortran API to functions detailed in ISO/IEC 9945-1:1990 Portable Operating System Interface (POSIX) - Part 1: System Application Program Interface (API) [C Language].

The functions in this module are from Section 4: Process Environment, plus gethostname from 4.3BSD.

Error handling is described in F90_UNIX_ERRNO. Note that for procedures with an optional ERRNO argument, if an error occurs and ERRNO is not present, the program will be terminated.

All the procedures in this module are generic; some are also specific (this may change in a future release).

3 Synopsis

Parameters
CLOCK_TICK_KIND, LONG_KIND, SC_STDIN_UNIT, SC_STDOUT_UNIT, SC_STDERR_UNIT, SC_ARG_MAX, SC_CHILD_MAX, SC_CLK_TCK, SC_NGROUPS_MAX, SC_SAVED_IDS, SC_VERSION, TIME_KIND.
Derived Types
TMS, UTSNAME.
Generic Procedures
CLK_TCK, CTERMID, GETARG, GETEGID, GETENV, GETEUID, GETGID, GETGROUPS, GETLOGIN, GETPGRP, GETPID, GETPPID, GETUID, IARGC, ISATTY, SETGID, SETPGID, SETSID, SETUID, SYSCONF, TIME, TIMES, TTYNAME, UNAME.
Note that many of these procedures are also specific; this may change in a future release.

4 Parameter Description

INTEGER(int32),PARAMETER :: clock_tick_kind
The integer kind used for clock ticks (see TIMES).

INTEGER(int32),PARAMETER :: id_kind
Integer kind for representing IDs; that is, users (uids), groups (gids), process groups (pgids) and processes (pids).

INTEGER(int32),PARAMETER :: long_kind
The integer kind corresponding to the C type ‘long’. This is not actually used in this module, but is suitable for use when declaring a variable to receive a value from SYSCONF.

INTEGER(int32),PARAMETER :: sc_stdin_unit, sc_stdout_unit, sc_stderr_unit,
    sc_arg_max, sc_child_max, sc_clk_tck, sc_job_control, sc_open_max,
    sc_ngroups_max, sc_saved_ids, sc_stream_max, sc_tzname_max, sc_version
Values used as arguments to SYSCONF. The following table describes the returned information from SYSCONF, this is not the value of the SC_* constant.
SC_STDIN_UNIT
The logical unit number for standard input (READ *,...); this is the same value as INPUT_UNIT in the standard intrinsic module ISO_FORTRAN_ENV.
SC_STDOUT_UNIT
The logical unit number for standard output (PRINT, WRITE(*,...)); this is the same value as OUTPUT_UNIT in the standard intrinsic module ISO_FORTRAN_ENV.
SC_STDERR_UNIT
The logical unit number on which errors are reported; this is the same value as ERROR_UNIT in the standard intrinsic module ISO_FORTRAN_ENV.
SC_ARG_MAX
Maximum length of arguments for the EXEC functions, in bytes, including environment data.
SC_CHILD_MAX
Maximum number of simultaneous processes for a single user.
SC_CLK_TCK
Number of clock ticks per second. (This is the same value returned by the CLK_TCK function).
SC_JOB_CONTROL
Value available only if job control is supported by the operating system.
SC_NGROUPS_MAX
Maximum number of simultaneous supplementary group IDs per process.
SC_OPEN_MAX
Maximum number of files open simultaneously by a single process.
SC_SAVED_IDS
Value available only if each process has a saved set-uid and set-gid.
SC_STREAM_MAX
Maximum number of logical units that can be simultaneously open. Not always available.
SC_TZNAME_MAX
Maximum number of characters for the name of a time zone.
SC_VERSION
Posix version number. This will be 199009 if the underlying operating system's C interface conforms to ISO/IEC 9945-1:1990.

INTEGER(int32),PARAMETER :: time_kind
The integer kind used for holding date/time values (see TIME).

5 Derived-Type Descriptions

TYPE tms
    INTEGER(clock_tick_kind) utime, stime, cutime, cstime
END TYPE
Derived type holding CPU usage time in clock ticks. UTIME and STIME contain CPU time information for a process, CUTIME and CSTIME contain CPU time information for its terminated child processes. In each case this is divided into user time (UTIME, CUTIME) and system time (STIME, CSTIME).

TYPE utsname
    CHARACTER(...) sysname, nodename, release, version, machine
END TYPE
Derived type holding data returned by UNAME. Note that the character length of each component is fixed, but may be different on different systems. The values in these components are blank-padded (if short) or truncated (if long). For further information see ISO/IEC 9945-1:1990.

6 Procedure Descriptions

PURE INTEGER(KIND=clock_tick_kind) FUNCTION clk_tck()
Returns the number of clock ticks in one second of CPU time (see TIMES).

PURE SUBROUTINE ctermid(s,lens)
    CHARACTER(*),OPTIONAL,INTENT(OUT) :: s
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: lens
If present, S is set to the filename of the controlling terminal. If present, LENS is set to the length of the filename of the controlling terminal. If S is longer than the filename of the controlling terminal it is padded with blanks; if S is shorter it is truncated — it is the user's responsibility to check the value of LENS to detect such truncation.

If the filename of the controlling terminal cannot be determined for any reason LENS (if present) will be set to zero and S (if present) will be blank.

SUBROUTINE getarg(k,arg,lenarg,errno)
    INTEGER(*),INTENT(IN) :: k
    CHARACTER(*),OPTIONAL,INTENT(OUT) :: arg
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: lenarg
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Accesses command-line argument number K, where argument zero is the program name. If ARG is present, it receives the argument text (blank-padded or truncated as appropriate if the length of the argument differs from that of ARG). If LENARG is present, it receives the length of the argument. If ERRNO is present, it receives the error status.

Note that if K is less than zero or greater than the number of arguments (returned by IARGC) error EINVAL (see F90_UNIX_ERRNO) is raised.

This procedure is very similar to the standard intrinsic procedure GET_COMMAND_ARGUMENT.

  PURE INTEGER(id_kind) FUNCTION getegid()
Returns the effective group number of the calling process.

SUBROUTINE getenv(name,value,lenvalue,errno)
    CHARACTER(*),INTENT(IN) :: name
    CHARACTER(*),OPTIONAL,INTENT(OUT) :: value
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: lenvalue
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Accesses the environment variable named by NAME. If VALUE is present, it receives the text value of the variable (blank-padded or truncated as appropriate if the length of the value differs from that of VALUE). If LENVALUE is present, it receives the length of the value. If ERRNO is present, it receives the error status.

If there is no such variable, error EINVAL (see F90_UNIX_ERRNO) is raised. Other possible errors include ENOMEM.

PURE INTEGER(id_kind) FUNCTION geteuid()
Returns the effective user number of the calling process.

PURE INTEGER(id_kind) FUNCTION getgid()
Returns the group number of the calling process.

SUBROUTINE getgroups(grouplist,ngroups,errno)
    INTEGER(id_kind),OPTIONAL,INTENT(OUT) :: grouplist(:)
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: ngroups
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Retrieves supplementary group number information for the calling process. If GROUPLIST is present, it is filled with the supplementary group numbers. If NGROUPS is present, it receives the number of supplementary group numbers. If ERRNO is present, it receives the error status.

If GROUPLIST is present but too small to contain the complete list of supplementary group numbers, error EINVAL (see F90_UNIX_ERRNO) is raised. The maximum number of supplementary group numbers can be found using SYSCONF (enquiry SC_NGROUPS_MAX); alternatively, ‘CALL GETGROUPS(NGROUPS=N)’ will reliably return the actual number in use.

PURE SUBROUTINE gethostname(name,lenname)
    CHARACTER(*),OPTIONAL,INTENT(OUT) :: name
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: lenname
This provides the functionality of 4.3BSD's gethostname. If NAME is present it receives the text of the standard host name for the current processor, blank-padded or truncated if appropriate. If LENNAME is present it receives the length of the host name. If no host name is available LENNAME will be zero.

PURE SUBROUTINE getlogin(s,lens)
    CHARACTER(*),OPTIONAL,INTENT(OUT) :: s
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: lens
Accesses the user name (login name) associated with the calling process. If S is present, it receives the text of the name (blank-padded or truncated as appropriate if the length of the login name differs from that of S). If LENS is present, it receives the length of the login name.

PURE INTEGER(id_kind) FUNCTION getpgrp()
Returns the process group number of the calling process.

PURE INTEGER(id_kind) FUNCTION getpid()
Returns the process number of the calling process.

PURE INTEGER(id_kind) FUNCTION getppid()
Returns the process number of the parent of the calling process.

PURE INTEGER(id_kind) FUNCTION getuid()
Returns the user number of the calling process.

PURE INTEGER(int32) FUNCTION iargc()
Returns the number of command-line arguments; this is the same value as the intrinsic function COMMAND_ARGUMENT_COUNT, except that it returns -1 if even the program name is unavailable (the intrinsic function erroneously returns the same value, 0, whether the program name is available or not).
SUBROUTINE isatty(lunit,answer,errno)
    INTEGER(*),INTENT(IN) :: lunit
    LOGICAL(*),INTENT(OUT) :: answer
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
ANSWER receives the value .TRUE. if and only if the logical unit identified by LUNIT is connected to a terminal.

If LUNIT is not a valid unit number or is not connected to any file, error EBADF (see F90_UNIX_ERRNO) is raised.

SUBROUTINE setgid(gid,errno)
    INTEGER(*),INTENT(IN) :: gid
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Sets the group number of the calling process to GID. For full details refer to section 4.2.2 of ISO/IEC 9945-1:1990.

If GID is not a valid group number, error EINVAL (see F90_UNIX_ERRNO) is raised. If the process is not allowed to set the group number to GID, error EPERM is raised.

SUBROUTINE setpgid(pid,pgid,errno)
    INTEGER(*),INTENT(IN) :: pid, pgid
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Sets the process group number of process PID (or, if PID is zero, the calling process) to PGID. For full details refer to section 4.3.3 of ISO/IEC 9945-1:1990.

Possible errors include EACCES, EINVAL, ENOSYS, EPERM, ESRCH (see F90_UNIX_ERRNO).

SUBROUTINE setsid(sid,errno)
    INTEGER(id_kind),OPTIONAL,INTENT(OUT) :: sid
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Creates a session and sets the process group number of the calling process. For full details refer to section 4.3.2 of ISO/IEC 9945-1:1990. If SID is present it receives the new session id (equal to the process id); if an error occurs it receives -1.

Possible errors include EPERM (see F90_UNIX_ERRNO).

SUBROUTINE setuid(uid,errno)
    INTEGER(*),INTENT(IN) :: uid
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Sets the user number of the calling process to UID. For full details refer to section 4.2.2 of ISO/IEC 9945-1:1990.

If UID is not a valid group number, error EINVAL (see F90_UNIX_ERRNO) is raised. If the process is not allowed to set the user number to UID, error EPERM is raised.

SUBROUTINE sysconf(name,val,errno)
    INTEGER(*),INTENT(IN) :: name
    INTEGER(*),INTENT(OUT) :: val
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Returns the value of a system configuration variable. The variables are named by integer PARAMETERs defined in this module, and are described in the Parameters section.

If NAME is not a valid configuration variable name, error EINVAL (see F90_UNIX_ERRNO) is raised. If VAL is too small an integer kind to contain the result, error ERANGE is raised; kind LONG_KIND is guaranteed to be big enough for all values.

SUBROUTINE time(itime,errno)
    INTEGER(time_kind),INTENT(OUT) :: itime
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
ITIME receives the operating system date/time in seconds since the Epoch.

INTEGER(KIND=clock_tick_kind) FUNCTION times(buffer)
    TYPE(tms),INTENT(OUT) :: buffer
This function returns the elapsed real time in clock ticks since an arbitrary point in the past, or -1 if the function is unavailable. BUFFER is filled in with CPU time information for the calling process and any terminated child processes.

If this function returns zero the values in BUFFER will still be correct but the elapsed-time timer was not available.

SUBROUTINE ttyname(lunit,s,lens,errno)
    INTEGER(*),INTENT(IN) :: lunit
    CHARACTER(*),OPTIONAL,INTENT(OUT) :: s
    INTEGER(int32),OPTIONAL,INTENT(OUT) :: lens
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Accesses the name of the terminal connected to the logical unit identified by LUNIT. If S is present, it receives the text of the terminal name (blank-padded or truncated as appropriate, if the length of the terminal name differs from that of S). If LENS is present, it receives the length of the terminal name. If ERRNO is present, it receives the error status.

If LUNIT is not a valid logical unit number, or is not connected, error EBADF (see F90_UNIX_ERRNO) is raised.

SUBROUTINE uname(name,errno)
    TYPE(UTSNAME),INTENT(OUT) :: name
    INTEGER(error_kind),OPTIONAL,INTENT(OUT) :: errno
Returns information about the operating system in NAME.

7 See Also

f90_unix_errno(3), intro(3), nag_modules(3), nagfor(1).

8 Bugs

Please report any bugs found to ‘support@nag.co.uk’ or ‘support@nag.com’, along with any suggestions for improvements.