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PM-GAWK(1) Utility Commands PM-GAWK(1) NAME persistent memory gawk - persistent data and functions SYNOPSIS truncate -s size heap.pma export GAWK_PERSIST_FILE=heap.pma gawk ... truncate -s size heap.pma GAWK_PERSIST_FILE=heap.pma gawk ... truncate -s size heap.pma alias pm='GAWK_PERSIST_FILE=heap.pma' pm gawk ... # succinct unset GAWK_PERSIST_FILE # disable persistence export GAWK_PERSIST_FILE=other_heap.pma # change heap rm heap.pma # delete heap DESCRIPTION Gawk 5.2 and later supports a persistent memory feature that can store script-defined variables and functions in a file for later use. The fea- ture, called pm-gawk, is described in GAWK: Effective AWK Programming and in Persistent Memory gawk User Manual. pm-gawk is activated by passing to gawk the name of an initially empty (all-zero-bytes) heap file, via the environment variable GAWK_PERSIST_FILE. pm-gawk retains script-defined variables and functions in the heap file for use in subsequent gawk invocations. pm-gawk offers at least two advantages compared with the existing rwarray extension: it offers constant-time (``O(1) time'') access to individual el- ements of persistent associative arrays, and it can store script-defined functions in addition to variables. EXAMPLES Demonstrate persistent variables: $ truncate -s 1G heap.pma # create heap file $ export GAWK_PERSIST_FILE=heap.pma # "ambient" env var $ gawk 'BEGIN { print ++i }' 1 $ gawk 'BEGIN { print ++i }' 2 $ gawk 'BEGIN { print ++i }' 3 To pass the environment variable on per-command basis: $ unset GAWK_PERSIST_FILE $ GAWK_PERSIST_FILE=heap.pma gawk 'BEGIN { print ++i }' 4 $ GAWK_PERSIST_FILE=heap.pma gawk 'BEGIN { print ++i }' 5 $ GAWK_PERSIST_FILE=heap.pma gawk 'BEGIN { print ++i }' 6 To reduce visual clutter of per-command environment variable passing: $ alias pm='GAWK_PERSIST_FILE=heap.pma' $ pm gawk 'BEGIN { print ++i }' 7 $ pm gawk 'BEGIN { print ++i }' 8 To refrain from activating persistence: $ unset GAWK_PERSIST_FILE $ gawk 'BEGIN { print ++i }' 1 $ gawk 'BEGIN { print ++i }' 1 To permanently ``forget'' the contents of the heap file: $ rm heap.pma ENVIRONMENT VARIABLES GAWK_PERSIST_FILE contains the name of a heap file where script-defined variables and functions are stored. If this environment variable is not visible to gawk, the persistence feature is not activated and gawk behaves in its traditional manner. VERSION INFORMATION Persistent memory gawk was first released in gawk 5.2. AUTHORS Arnold Robbins, the maintainer of gawk, implemented pm-gawk using a persis- tent memory allocator (pma) provided by Terence Kelly. An earlier proof- of-concept prototype of persistent gawk was developed by Haris Volos, Zi Fan Tan, and Jianan Li using a fork of the official gawk sources. CAVEATS The GNU/Linux CIFS filesystem is known to cause problems for the persistent memory allocator. Do not use a backing file on such a filesystem with pm- gawk. pm-gawk produces a warning if the current version of gawk doesn't match the one that was first used with a particular backing storage file. BUG REPORTS Follow the procedures in GAWK: Effective AWK Programming and in Persistent Memory gawk User Manual. For suspected bugs related to persistence (as op- posed to other non-persistence-related gawk bugs) please also send e-mail to Terence Kelly at one or more of these addresses: tpkelly@acm.org, tp- kelly@eecs.umich.edu, or tpkelly@cs.princeton.edu. SEE ALSO gawk(1), GAWK: Effective AWK Programming, and Persistent Memory gawk User Manual. The two manuals should be available in the Info subsystem if Info installed on your system. See https://web.eecs.umich.edu/~tpkelly/pma/ for the latest source code and manual. COPYING PERMISSIONS Copyright (C) 2022 Terence Kelly. Permission is granted to make and distribute verbatim copies of this manual page provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this man- ual page under the conditions for verbatim copying, provided that the en- tire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual page into another language, under the above conditions for modified ver- sions, except that this permission notice may be stated in a translation approved by the Foundation. Free Software Foundation June 01 2025 PM-GAWK(1)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | ENVIRONMENT VARIABLES | VERSION INFORMATION | AUTHORS | CAVEATS | BUG REPORTS | SEE ALSO | COPYING PERMISSIONS
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