```{index} single: sysconf; POSIX function ``` ```{index} single: POSIX::sysconf; Perl function ``` # sysconf Runtime system configuration value for the given `_SC_*` name. ## Synopsis ```perl use POSIX qw(sysconf _SC_OPEN_MAX _SC_PAGESIZE); my $max_fd = sysconf(_SC_OPEN_MAX); ``` ## What you get back The configured value, or `-1` if the option is not supported (in which case `$!` may or may not be set — distinguish by checking `$!` before and after). ## Differences from upstream Fully compatible with upstream POSIX.