Contents

System Interface (sys)

Module: utils_sys

Overview

Provides platform-independent system functions for SPEX, including date/time operations, environment variable access, and system information retrieval.

Key Features

  • Cross-platform system interface

  • Date and time functions

  • Environment variable access

  • System information retrieval

  • No external dependencies

API Reference

Functions

sys_datum

sys_datum(datum)

Get current date and time from the operating system

Parameters:

datum – Formatted date and time string (character*24, output)

Returns:

None

Returns system date and time in standardized 24-character format.

Format: DD-MMM-YYYY HH:MM:SS GMT

Example: 15-JAN-2024 14:30:45 GMT

sys_getenv

sys_getenv(ename, evalue, l)

Retrieve environment variable value

Parameters:

  • ename – Environment variable name (character(*), input)

  • evalue – Environment variable value (character(*), output)

  • l – Length of returned value (integer, output)

Returns:

None

Case-sensitive environment variable lookup.

Returns actual length of value for proper string handling.

Usage Examples

Get Current Date/Time

use utils_sys
character(len=24) :: current_time

! Get current system time
call sys_datum(current_time)
write(*,*) 'Current time:', trim(current_time)

Read Environment Variables

use utils_sys
character(len=256) :: spex_path
integer :: path_length

! Get SPEX installation path
call sys_getenv('SPEX4', spex_path, path_length)
if (path_length > 0) then
   write(*,*) 'SPEX installed at:', trim(spex_path(1:path_length))
else
   write(*,*) 'SPEX4 not set'
endif

System Information

use utils_sys
character(len=24) :: timestamp
character(len=256) :: username, home_dir
integer :: username_len, home_len

! Get system information
call sys_datum(timestamp)
call sys_getenv('USER', username, username_len)
call sys_getenv('HOME', home_dir, home_len)

write(*,*) 'System Info:'
write(*,*) '  Time: ', trim(timestamp)
write(*,*) '  User: ', trim(username(1:username_len))
write(*,*) '  Home: ', trim(home_dir(1:home_len))

Notes

Platform Independence

  • Abstracts operating system differences

  • Consistent behavior across Unix/Linux/Windows

  • Handles environment variable syntax differences

Error Handling

  • No explicit error codes

  • Returns empty strings for unset variables

  • Length parameter helps detect unset variables

Performance

  • Fast system calls

  • Minimal overhead

  • Suitable for frequent calls

Best Practices

  1. Check length parameter to detect unset variables

  2. Use trim() on returned strings

  3. Handle unset variables gracefully

  4. Use for logging and debugging information

See Also