Other Environment Variables (The GNU Awk User’s Guide)
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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_READ_TIMEOUT
- Specifies the time, in milliseconds, for
gawk
to wait for input before returning with an error. See section Reading Input with a Timeout. GAWK_SOCK_RETRIES
- Controls the number of times
gawk
attempts to retry a two-way TCP/IP (socket) connection before giving up. See section Using gawk for Network Programming. Note that when nonfatal I/O is enabled (see section Enabling Nonfatal Output),gawk
only tries to open a TCP/IP socket once. POSIXLY_CORRECT
- Causes
gawk
to switch to POSIX-compatibility mode, disabling all traditional and GNU extensions. See section Command-Line 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, andgawk
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. 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_MSG_SRC
- If this variable exists,
gawk
includes the file name and line number within thegawk
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 thebindtextdomain()
function whengawk
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 causegawk
to be slower. Its purpose is to help isolate differences between the two regexp matchers thatgawk
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 themtrace()
library calls from the GNU C library to help track down possible memory leaks.
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