info gawk

2.5.2 Other Environment Variables

A number of other environment variables affect gawk’s behavior, but they are more specialized. Those in the following list are meant to be used by regular users.

POSIXLY_CORRECT: Causes gawk to switch POSIX compatibility mode, disabling all traditional and GNU extensions. See section Command-Line Options.
GAWK_SOCK_RETRIES: Controls the number of time gawk will attempt to retry a two-way TCP/IP (socket) connection before giving up. See section Using gawk for Network Programming.
GAWK_MSEC_SLEEP: Specifies the interval between connection retries, in milliseconds. On systems that do not support the usleep() system call, the value is rounded up to an integral number of seconds.

The environment variables in the following list are meant for use by the gawk developers for testing and tuning. They are subject to change. The variables are:

AVG_CHAIN_MAX: The average number of items gawk will maintain on a hash chain for managing arrays.
AWK_HASH: If this variable exists with a value of ‘gst’, gawk will switch to using the hash function from GNU Smalltalk for managing arrays. This function may be marginally faster than the standard function.
AWKREADFUNC: If this variable exists, gawk switches to reading source files one line at a time, instead of reading in blocks. This exists for debugging problems on filesystems on non-POSIX operating systems where I/O is performed in records, not in blocks.
GAWK_NO_DFA: If this variable exists, gawk does not use the DFA regexp matcher for “does it match” kinds of tests. This can cause gawk to be slower. Its purpose is to help isolate differences between the two regexp matchers that gawk uses internally. (There aren’t supposed to be differences, but occasionally theory and practice don’t coordinate with each other.)
GAWK_STACKSIZE: This specifies the amount by which gawk should grow its internal evaluation stack, when needed.
TIDYMEM: If this variable exists, gawk uses the mtrace() library calls from GNU LIBC to help track down possible memory leaks.

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