File: gawk.info,  Node: Other Environment Variables,  Prev: AWKLIBPATH Variable,  Up: Environment Variables

2.5.3 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:

'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.

'GAWK_PERSIST_FILE'
     Specifies the backing file to use for persistent storage of
     'gawk''s variables and arrays.  *Note Persistent Memory::.

'GAWK_READ_TIMEOUT'
     Specifies the time, in milliseconds, for 'gawk' to wait for input
     before returning with an error.  *Note Read Timeout::.

'GAWK_SOCK_RETRIES'
     Controls the number of times 'gawk' attempts to retry a two-way
     TCP/IP (socket) connection before giving up.  *Note TCP/IP
     Networking::.  Note that when nonfatal I/O is enabled (*note
     Nonfatal::), 'gawk' only tries to open a TCP/IP socket once.

'PMA_VERBOSITY'
     Controls the verbosity of the persistent memory allocator.  *Note
     Persistent Memory::.

'POSIXLY_CORRECT'
     Causes 'gawk' to switch to POSIX-compatibility mode, disabling all
     traditional and GNU extensions.  *Note Options::.

   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:

'AWKBUFSIZE'
     This variable only affects 'gawk' on POSIX-compliant systems.  With
     a value of 'exact', 'gawk' uses the size of each input file as the
     size of the memory buffer to allocate for I/O. Otherwise, the value
     should be a number, and 'gawk' uses that number as the size of the
     buffer to allocate.  (When this variable is not set, 'gawk' uses
     the smaller of the file's size and the "default" blocksize, which
     is usually the filesystem's I/O blocksize.)

'AWK_HASH'
     If this variable exists with a value of 'gst', 'gawk' switches to
     using the hash function from GNU Smalltalk for managing arrays.
     With a value of 'fnv1a', 'gawk' uses the FNV1-A hash function
     (http://www.isthe.com/chongo/tech/comp/fnv/index.html).  These
     functions 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_MSG_SRC'
     If this variable exists, 'gawk' includes the file name and line
     number within the 'gawk' source code from which warning and/or
     fatal messages are generated.  Its purpose is to help isolate the
     source of a message, as there are multiple places that produce the
     same warning or error message.

'GAWK_LOCALE_DIR'
     Specifies the location of compiled message object files for 'gawk'
     itself.  This is passed to the 'bindtextdomain()' function when
     'gawk' starts up.

'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.

'INT_CHAIN_MAX'
     This specifies intended maximum number of items 'gawk' will
     maintain on a hash chain for managing arrays indexed by integers.

'STR_CHAIN_MAX'
     This specifies intended maximum number of items 'gawk' will
     maintain on a hash chain for managing arrays indexed by strings.

'TIDYMEM'
     If this variable exists, 'gawk' uses the 'mtrace()' library calls
     from the GNU C library to help track down possible memory leaks.
     This cannot be used together with the persistent memory allocator.