AllAboutGetline
//Editor's notes: The article was originally posted on the comp.lang.awk newsgroup, and can still be . . . If you need the input record split into separate fields, just call "split()" to do that. ===Caveats . . .
16K - last updated 2009-02-15 22:14 UTC by waldner
awk1page
an awk program is a series of //pattern { actions }// statements;\\ ie if the input line matchs pattern . . . the string ''abc''. Lines are split into fields separated by whitespace - $1 is the first field; . . . those lines where "awk" appears in the first field. $1 ~ /awk/ { print $0; } }}} An omited pattern . . . sum } }}} To also find the maximum value of field $1: {{{awk { sum = sum + $1 } $1 > max { max . . .
2K - last updated 2012-03-18 22:22 UTC by g0pher
AwkFeatureComparison
This page lists which awk implementations support which features. Additions and corrections are very . . . (both with ~// and "")|yes (extra field with ~//)|yes with "", no with ~//|no|no|unknown|yes . . . with "", no with ~//|yes (extra field with ~//)|yes| |=sub()/gsub() can replace the . . .
4K - last updated 2015-04-27 13:23 UTC by pgas
AwkGuide
** Work in Progress ** {{{ import from Mark Hobley's wiki }}} <toc> ---- == Overview * [[Overview]] . . . * [[escape sequence]]s * [[expression]]s * [[field]]s * [[field reference]] operator * [[FS|field . . .
4K - last updated 2011-08-14 15:57 UTC by markhobley
AwkOnWindowsHowto
AwkOnWindowsHowto\\ rough cut - needs edit {{{ 3) awk command line switches/usage from a win32 cmd.exe . . . -f - read the program from stdin -F fs set field separator FS to value of fs (nojoy -F "" to set . . .
3K - last updated 2010-10-24 07:44 UTC by g0pher
AwkTips
<toc> ---- == Be idiomatic! In this paragraph, we give some hints on how to write more idiomatic . . . '$2 == "foo"' # prints lines where the second field is "foo" awk 'NF >= 6' # prints lines with . . . 6 or more fields awk '/foo/ && /bar/' # prints lines . . . lines, where NF==0) awk 'NF--' # removes last field and prints the line awk '$0 = NR" "$0' # prepends . . . innocuous operation like removing the first 3 fields. {{{ $ LC_ALL=en_US.utf8 awk --re-interval '{sub(/^([^[:space:]]+[[:space:]]+){3}/,"")}1' . . .
31K - last updated 2009-03-24 16:54 UTC by waldner
BEGIN
== Begin Blocks The [[awk]] programming language allows us to use **begin blocks** and **end blocks** . . . such as the [[RS|record separator]] and [[FS|field separator]], but they can contain other commands: . . . "The awk parser" # Print the title # Set the field separator to a colon FS = ":" } }}} == Behaviour . . .
3K - last updated 2013-04-11 14:25 UTC by 92.40.253.171.threembb.co.uk
Columnate
This script columnates the input file, so that columns line up like in the GNU column(1) command. Its . . . file, keeps track of the maximum width of each field, and saves all the lines/records. At the END, . . . max[f] = len # an array of maximum field widths } } END { for(nr=1; nr<=NR; nr++) { . . . nf = split(line[nr], fields) for (f=1; f<nf; f++) printf "%-*s", max[f]+2, . . . fields[f] print fields[f] # the last field need not . . .
1K - last updated 2009-02-28 21:32 UTC by h-67-101-152-180.nycmny83.dynamic.covad.net
comp.lang.awk FAQ
This material of this faq originates from the comp.lang.awk FAQ that you can find there: * http://www.faqs.org/faqs/computer-lang/awk/faq/ . . . split the first record? <include "WhenAreTheFieldsSet"> [[http://awk.freeshell.org/?action=edit;id=WhenAreTheFieldsSet| . . .
8K - last updated 2009-03-04 12:42 UTC by pgas
CookBook
<toc> ---- Just started, the aim of this page is to collect small pieces of code that illustrate . . . specific problems. == Looping on all the fields(columns) of a Record(lines) <include "LoopOnFields"> . . . [[http://awk.freeshell.org/?action=edit;id=LoopOnFields| Edit this answer]] ---- == How to test if an . . .
1K - last updated 2009-04-14 09:03 UTC by 216.162.199.202
dollar
== Prefixing field numbers == The dollar symbol can be used to prefix [[field]] numbers: == Regular expression . . .
1K - last updated 2010-11-28 10:46 UTC by markhobley
dollarint
A [[dollar]] sign and followed by an [[integer]] are used to refer to [[field]]s within the current [[record]]: . . . {{{ awk { print $3 } # output field number three }}} Though you might consider $3 . . . it's not exactly true, in fact $ is the field reference operator and 3 is just a number that . . . tells awk you want to reference the third field. They behave a bit like an array ie where with . . . an array you would write fields[1] in awk you write $1 If you know C it behaves . . .
3K - last updated 2011-06-25 05:28 UTC by pgas
Features of awk
The [[awk]] utility: * treats lines of a text as database records, which can be divided into fields. . . .
1K - last updated 2011-05-27 15:33 UTC by markhobley
field
In [[awk]] all [[input]] is separated into [[record]]s and each [[record]] is further divided into fields. . . . == Fields are referenced using special variables == Within . . . the [[awk]] script, each field can be referenced by using [[dollarint]] operator. . . . {{{ awk { print $3 } # output field number three { print $12 } # output field number . . .
1K - last updated 2011-06-25 05:31 UTC by pgas
field reference
== The field reference operator == The [[dollar]] symbol acts as a unary *field reference operator* and . . . by a number or expression that gives a [[field]] number within the [[current record]]: {{{ { . . . print $3 } # output field number three }}} === Field numbers are not limited . . . the positional parameters in the Unix shell, [[field]] numbers are not limited to single digits: {{{ . . . { print $123 } # output field number 123 }}} ==== Using a variable name to . . .
2K - last updated 2011-06-28 09:12 UTC by markhobley
FieldReference
$ is the "field reference" operator in AWK. It references the field in the current input record given . . . or constant. E.g. if you want to print the first field, the following are equivalent: {{{ # print the . . . first field using the '$' operator and a constant. print . . . $i; }}} The power of awk is in learning to use field references, some further examples: {{{ # print . . . both the value of i, and the field at $i.. print i, $i; # print the field at $i, . . .
1K - last updated 2009-01-03 01:51 UTC by fcr
FileAndBitJoinClone
== Problem Description This was difficult to hash out. Eventually the task was described as, "for each . . . is always equal to NR - that is, the first field on each line of bit.txt is simply the line number . . . that bit.txt is already sorted on the first # field. Since that first field is supposed to be the . . .
7K - last updated 2009-03-08 16:26 UTC by waldner
FIXES
[[FIXES]] revised: . . . the same changes for field-splitting if FS is "".\\ \\ added nextfile, as . . .
6K - last updated 2014-01-15 23:17 UTC by g0ph3r
Frequently Asked Questions
Some entries of this page have been copied from the [[comp.lang.awk_FAQ]]([[http://awk.freeshell.org/comp.lang.awk_FAQ#toc29|Credits]]) . . . <toc> ---- == How do I print a RangeOfFields, eg from field 2 to the end? <include "RangeOfFields"> . . . Edit this answer]] ---- == How do I print the . . . LastField or the n'th field in a record? <include "LastField"> . . . [[http://awk.freeshell.org/?action=edit;id=LastField| Edit this answer]] ---- == I'm trying to print . . .
3K - last updated 2015-09-08 08:46 UTC by pgas
FS
= Field Separator = The [[special variable]] FS is a field separator that is used to determine how [[awk]] . . . will split each [[record]] into [[field]]s. == The single space field separator == The . . . default value for the field separator is a single space character. In data . . . files, fields are often separated by multiple whitespace characters, . . . interpreted as separators delimiting an empty field. Note that only a single space is treated as . . .
5K - last updated 2013-02-19 21:45 UTC by markhobley
gawkism
Gawkisms are non portable syntax components that do not work with some awk implementations. The use of . . . array * [[ERRNO]] * [[exponent]] operator * [[FIELDWIDTHS]] * [[gensub]] function * [[hexadecimal]] . . .
2K - last updated 2011-05-19 22:29 UTC by markhobley
input
The [[awk]] utility can take its input from [[standard input]] or from [[file]]s. If no input files are . . . of data). === Records are further divided into fields === In awk, [[record]]s are further divided . . . into [[field]]s, making them easy to manage, because processing . . . can take place against a particular data [[field]]. == Taking input from files == The [[awk]] . . . | A control variable that specifies the input field separator | [[NF]] | An informative variable . . .
2K - last updated 2011-05-19 22:40 UTC by markhobley
LargestAccurateNumber
Most [[awk]] implementations use floating point double precision to represent every kind of numeric value. . . . not "mantissa". This is because the fraction field is interpreted differently in different circumstances. . . . +0 and -0. Thanks, IEEE!) If the exponent field has **any** non-zero bits, it is assumed that . . .
3K - last updated 2013-04-12 14:52 UTC by ttmrichter
LastField
awk performs a number of actions automatically when it parses lines: it updates the variable NF, which . . . contains the number of fields on a line; and it parses the record into a series . . . of fields which are accessible via the variables $1, $2, . . . it's not exactly true, in fact $ is the field reference operator and 1 is just a number that . . . tells awk you want to reference the first field. They behave a bit like an array ie where with . . .
2K - last updated 2009-02-05 22:43 UTC by firebush.stsci.edu
LoopOnFields
Fields are numbered from 1 to NF, so you can easily use a for loop, and the derefence operator, for instance . . . to print each field matching foo: {{{ awk for (i=1;i<=NF;i++) . . .
1K - last updated 2009-03-17 21:09 UTC by waldner
LshalOutputParser
=== Problem Specification 10:50 <Thanatermesis> i want to obtain the model of the disk, for example, . . . i have think to use awk in a way that the field separator be every line, and the record separator . . .
3K - last updated 2008-06-27 16:22 UTC by gnomon
NF
= Number of Fields = The [[special variable]] NF holds the number of [[field]]s in the [[current record]]. . . . $NF is used to refer to the last [[field]] in the [[current record]]. The following [[script]] . . . outputs the first and last [[field]] from each [[record]]: {{{ awk '{ print $1,$NF . . .
1K - last updated 2011-05-28 15:14 UTC by markhobley
PrimeNumberSieve
This is the standard sieve of Eratosthenes implemented in portable awk. The running time of the bare . . . in the below code is that the former uses awk's fields to store values and the latter uses a standard . . . exceptions, as per the spec). Arrays, numbered fields and the {{{substr()}}} built-in are the only . . . of the three, only arrays and numbered fields offer O(1) assignment as well; and of those . . . two, numbered fields //ought// to have a lower constant factor than . . .
4K - last updated 2008-06-19 05:56 UTC by gnomon
PrintASingleQuote
This question gets asked often enough that it deserves its own answer. This common question doesn't actually . . . with awk's literal string syntax and the "$" field reference operator. ==== Hex Escapes: Bad Juju . . .
5K - last updated 2015-07-05 09:45 UTC by pitman
PureEvil
Not related to awk, just for fun. Some deliberately obfuscated and evil commands: {{{ sh # squeeze the . . . bar foo" | sed ':;;\;foo;s;;;;t;' #cut the first field a string separated by : (like cut -d: -f1) echo . . .
1K - last updated 2011-09-08 14:00 UTC by pgas
RangeOfFields
Printing a range of fields - all fields but the first, for examples, or fields 3 through 8 - is a surprisingly . . . fiddly little problem. ==== No field offsets are stored Although awk performs field . . . can, for example, assign an empty string to the fields preceding and following the range that you want . . . awk to recompute the line adding OFS between the field, including the now empty fields at the beginning . . . * 2) }}}, another possibility is to shift the fields and adjust NF eg to keep the fields 3 to 8: . . .
10K - last updated 2015-09-08 09:52 UTC by pgas
record
The awk utility divides its [[input]] into records and [[field]]s. == By default, each line of input . . .
1K - last updated 2011-05-17 23:52 UTC by markhobley
RS
= Record Separator = The [[special variable]] RS is a record separator that is used to determine how . . . are being used, each line is treated as a field of data, and each [[record]] is separated by . . . The newline character will always act as a field separator when multiline records are being. There . . . is possible to use the split function to extract fields as desired. == Setting the record separator . . .
3K - last updated 2013-02-19 23:11 UTC by markhobley
SizeOfSplit
How many elements were created by split()? When I do a split on a field, e.g., {{{ awk split($1,x,"string") . . .
1K - last updated 2008-11-18 12:35 UTC by pgas
special variable
Some [[variable]] names have a special meaning to the awk interpreter. == List of special variables == . . . | A control variable that specifies the input field separator | [[NF]] | An informative variable . . . that provides the number of fields within the current record | [[NR]] | An informative . . . | A control variable that specifies the output field separator | [[ORS]] | A control variable that . . .
2K - last updated 2011-06-25 05:46 UTC by pgas
symbol
| *Symbol* | *Name* | *Purpose* | !! | [[pling]] | logical NOT | " | [[doublequote]] | | # | [[hash]] . . . | prefixes comments | $ | [[dollar]] | field reference operator and regular expression anchor . . .
2K - last updated 2013-02-19 14:26 UTC by markhobley
Transpose
To transpose a N rows x M columns file into a M rows x N column file, one approach is to read the whole . . . and columns (the example assumes comma separated fields; adapt to your real data): {{{ awk BEGIN{FS=","} . . .
1K - last updated 2011-03-20 06:53 UTC by ppp089210038204.dsl.hol.gr
WartAndWishList
Awk is a wonderful language! That said, there are a few annoying bits... == The Good * well-documented . . . quite difficult to map back from the auto-split fields to positions in a given record, since awk only . . . exposes the results of its field parsing and hides the offsets (but look at the . . .
7K - last updated 2009-04-13 18:39 UTC by goedel
WhenAreTheFieldsSet
Basically, you should set FS before it may be called upon to split $0 into fields. Once awk encounters . . . too late. Some awk implementations set the fields at the beginning of the block, and don't re-parse . . .
1K - last updated 2008-12-15 12:46 UTC by pgas
XMLScraping
You cannot easily parse xml with awk. But there are several tricks to scrap an xml file: <toc> . . . </tag> are on the same line You can use a Field separator matching the tag: </?tag>, the . . . line will then look like {{{ field1 FS field2 FS field3 }}} where the first FS is . . . the second one is the closing tag, extracting field2 is then easy: {{{ sh awk -F'</?tag>' 'NF>1{print . . .
2K - last updated 2011-11-23 15:06 UTC by pgas
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