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
feature, called pm-gawk, is described in GAWK: Effective AWK Program-
ming 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_PER-
SIST_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 rwar-
ray extension: it offers constant-time (``O(1) time'') access to indi-
vidual elements 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
persistent memory allocator (pma) provided by Terence Kelly. An ear-
lier 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 per-
sistent memory allocator. Do not use a backing file on such a filesys-
tem with pm-gawk.
BUG REPORTS
Follow the procedures in GAWK: Effective AWK Programming and in Persis-
tent Memory gawk User Manual. For suspected bugs related to persis-
tence (as opposed 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, tpkelly@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 © 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
manual page under the conditions for verbatim copying, provided that
the entire 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 man-
ual page into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a trans-
lation approved by the Foundation.
Free Software Foundation Nov 17 2022 PM-GAWK(1)
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