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Copy pathRegular_Expressions.sh
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Copy pathRegular_Expressions.sh
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340 lines (171 loc) · 8.49 KB
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## Syntax and variable assignment
printf 'spared no one\ngrasped\nspar\n' | awk '/ed/'
printf 'spared no one\ngrasped\nspar\n' | awk 'BEGIN{r = @/ed/} $0 ~ r'
## String Anchors
cat anchors.txt
awk '/^sp/' anchors.txt
awk '/ar$/' anchors.txt
printf 'spared no one\npar\nspar\n' | awk '{sub(/^spar$/, "123")} 1'
printf 'spared no one\ngrasped\nspar\n' | awk '{gsub(/^/, "* ")} 1'
printf 'spared no one\ngrasped\nspar\n' | awk '!/ /{gsub(/$/, ".")} 1'
## Word Anchors
cat anchors.txt
awk '/\<par/' anchors.txt
awk '/par\>/' anchors.txt
awk 'gsub(/\<par\>/, "***")' anchors.txt
## Opposite Word Anchor
awk '/\Bpar\B/' anchors.txt
awk '/\Bpar/' anchors.txt
awk '/par\B/' anchors.txt
echo 'copper' | awk '{gsub(/\y/, ":")} 1'
echo 'copper' | awk '{gsub(/\B/, ":")} 1'
## Combining conditions
awk '/^b/ && !/at/' table.txt
awk '$1 ~ /low/ || $NF<0' table.txt
## Alternation
awk '/\<par\>|s$/' anchors.txt
echo 'cats dog bee parrot foxed' | awk '{gsub(/cat|dog|fox/, "--")} 1'
## Alternation precedence
echo 'cats dog bee parrot foxed' | awk '{sub(/bee|parrot|at/, "--")} 1'
echo 'cats dog bee parrot foxed' | awk '{sub(/parrot|at|bee/, "--")} 1'
echo 'spared party parent' | awk '{sub(/spa|spared/, "**")} 1'
echo 'spared party parent' | awk '{sub(/spared|spa/, "**")} 1'
echo 'spared party parent' | perl -pe 's/spa|spared/**/'
## Grouping
printf 'red\nreform\nread\narrest\n' | awk '/reform|rest/'
printf 'red\nreform\nread\narrest\n' | awk '/re(form|st)/'
awk '/\<par\>|\<part\>/' anchors.txt
awk '/\<(par|part)\>/' anchors.txt
awk '/\<par(|t)\>/' anchors.txt
## Matching the metacharacters
printf 'a^2 + b^2 - C*3\nd = c^2' | awk '/b\^2/'
echo '(a*b) + c' | awk '{gsub(/\(|)/, "")} 1'
printf '%s\n' '\learn\by\example' | awk '{gsub(/\\/, "/")} 1'
## Using string literal as a regexp
p='/home/learnbyexample/reports'
echo "$p" | awk '{sub(/\/home\/learnbyexample\//, "~/")} 1'
echo "$p" | awk '{sub("/home/learnbyexample/", "~/")} 1'
printf '/home/joe/1\n/home/john/1\n' | awk '/\/home\/joe\//'
printf '/home/joe/1\n/home/john/1\n' | awk '$0 ~ "/home/joe/"'
awk 'gsub("\<par\>", "X")' anchors.txt
awk 'gsub("\\<par\\>", "X")' anchors.txt
awk 'gsub(/\<par\>/, "X")' anchors.txt
printf '%s\n' '\learn\by\example' | awk '{gsub("\\\\", "/")} 1'
printf '%s\n' '\learn\by\example' | awk '{gsub(/\\/, "/")} 1'
## The dot meta character
echo 'tac tin cot abc:tyz excited' | awk '{gsub(/c.t/, "-")} 1'
printf '42\t3500\n' | awk '{gsub(/.3./, ":")} 1'
awk 'BEGIN{s="abc\nxyz"; sub(/c.x/, " ", s); print s}'
## Quantifiers
echo 'fed fold fe:d feeder' | awk '{gsub(/\<fe.?d\>/, "X")} 1'
awk '/\<part?\>/' anchors.txt
echo 'par part parrot parent' | awk '{gsub(/par(ro)?t/, "X")} 1'
echo 'par part parrot parent' | awk '{gsub(/par(en|ro)?t/, "X")} 1'
echo 'apple \< fig ice < apple cream <' | awk '{gsub(/\\?</, "\\<")} 1'
echo 'fd fed fod fe:d feeeeder' | awk '{gsub(/fe*d/, "X")} 1'
echo '3111111111125111142' | awk '{gsub(/1*2/, "-")} 1'
echo 'fd fed fod fe:d feeeeder' | awk '{gsub(/fe+d/, "X")} 1'
echo '3111111111125111142' | awk '{gsub(/1+4?2/, "-")} 1'
echo 'ac abc abbc abbbc abbbbbbbbc' | awk '{gsub(/ab{1,4}c/, "X")} 1'
echo 'ac abc abbc abbbc abbbbbbbbc' | awk '{gsub(/ab{3,}c/, "X")} 1'
echo 'ac abc abbc abbbc abbbbbbbbc' | awk '{gsub(/ab{,2}c/, "X")} 1'
echo 'ac abc abbc abbbc abbbbbbbbc' | awk '{gsub(/ab{3}c/, "X")} 1'
echo 'a{5} = 10' | awk '{sub(/a\{5}/, "x")} 1'
echo 'report_{a,b}.txt' | awk '{sub(/_{a,b}/, "_c")} 1'
## Conditional AND
echo 'Error: not a valid input' | awk '/Error.*valid/'
echo 'two cats and a dog' | awk '{gsub(/cat.*dog|dog.*cat/, "pets")} 1'
echo 'two dogs and a cat' | awk '{gsub(/cat.*dog|dog.*cat/, "pets")} 1'
## Longest match wins
echo 'foot' | awk '{sub(/f.?o/, "X")} 1'
echo 'car bat cod map scat dot abacus' | awk '{sub(/.*/, "X")} 1'
echo 'fig123312apple' | awk '{sub(/g(1|2|3)+(12apple)?/, "X")} 1'
echo 'fig123312apple' | perl -pe 's/g(1|2|3)+(12apple)?/X/'
echo 'car bat cod map scat dot abacus' | awk '{sub(/.*b/, "-")} 1'
echo 'car bat cod map scat dot abacus' | awk '{sub(/b.*t/, "-")} 1'
echo 'car bat cod map scat dot abacus' | awk '{sub(/b.*at/, "-")} 1'
echo 'car bat cod map scat dot abacus' | awk '{sub(/a.*m*/, "-")} 1'
## Character classes
printf 'cute\ncat\ncot\ncoat\ncost\nscuttle\n' | awk '/c[ou]t/'
printf 'meeting\ncute\nboat\nat\nfoot\n' | awk '/.[aeo]t/'
echo 'no so in to do on' | awk '{gsub(/\<[sot][on]\>/, "X")} 1'
awk '/^[on]{2,}$/' words.txt
## Character class metacharacters
echo 'Sample123string42with777numbers' | awk '{gsub(/[0-9]+/, "-")} 1'
echo 'coat Bin food tar12 best' | awk '{gsub(/\<[a-z0-9]+\>/, "X")} 1'
echo 'road i post grip read eat pit' | awk '{gsub(/\<[p-z][a-z]*\>/, "X")} 1'
echo '23 154 12 26 34' | awk '{gsub(/\<[12][0-9]\>/, "X")} 1'
echo '0501 035 154 12 26 98234' | awk '{gsub(/\<0*[1-9][0-9]{2,}\>/, "X")} 1'
echo 'Sample123string42with777numbers' | awk '{gsub(/[^0-9]+/, "-")} 1'
echo 'apple:123:banana:cherry' | awk '{sub(/(:[^:]+){2}$/, "")} 1'
echo 'I like "mango" and "guava"' | awk '{gsub(/"[^"]+"/, "X")} 1'
printf 'tryst\nfun\nglyph\npity\nwhy\n' | awk '!/[aeiou]/'
printf '%s\n' 'load;err_msg--\/ant,r2..not' | awk '{gsub(/\W+/, "|")} 1'
printf 'hi \v\f there.\thave \ra nice\t\tday\n' | awk '{gsub(/\s+/, " ")} 1'
printf '%s\n' 'w=y\x+9*3' | awk '{gsub(/[\w=]/, "")} 1'
printf '%s\n' '42\d123' | awk '{gsub(/\d+/, "-")} 1'
printf '%s\n' '42\d123' | perl -pe 's/\d+/-/g'
## Named character sets
s='err_msg xerox ant m_2 P2 load1 eel'
echo "$s" | awk '{gsub(/\<[[:lower:]]+\>/, "X")} 1'
echo "$s" | awk '{gsub(/\<[[:lower:]_]+\>/, "X")} 1'
echo "$s" | awk '{gsub(/\<[[:alnum:]]+\>/, "X")} 1'
echo ',pie tie#ink-eat_42' | awk '{gsub(/[^[:punct:]]+/, "")} 1'
## Matching character class metacharacters literally
echo 'ab-cd gh-c 12-423' | awk '{gsub(/[a-z-]{2,}/, "X")} 1'
echo 'ab-cd gh-c 12-423' | awk '{gsub(/[a-z\-0-9]{2,}/, "X")} 1'
printf 'int a[5]\nfig\n1+1=2\n' | awk '/[=]]/'
printf 'int a[5]\nfig\n1+1=2\n' | awk '/[]=]/'
echo 'int a[5].y' | awk '{gsub(/[x[y.]/, "")} 1'
printf 'int a[5]\nfig\n1+1=2\nwho]' | awk '/[][]/'
echo 'f*(a^b) - 3*(a+b)/(a-b)' | awk '{gsub(/a[+^]b/, "c")} 1'
echo 'int a[5]' | awk '/[x[.y]/'
echo 'int a[5]' | awk '/[x[y.]/'
## Escape sequences
printf 'apple\tbanana\tcherry\n' | awk '{gsub(/\t/, " ")} 1'
printf 'a\t\r\fb\vc\n' | awk '{gsub(/[\t\v\f\r]+/, ":")} 1'
echo "universe: '42'" | awk '{gsub(/\x27/, "")} 1'
printf 'acorn\ncot\ncat\ncoat\n' | awk '/\x5eco/'
echo 'hello world' | awk '{sub(/.*/, "[&]")} 1'
echo 'hello world' | awk '{sub(/.*/, "[\x26]")} 1'
echo 'read' | awk '{sub(/\d/, "l")} 1'
awk 'BEGIN{print "\u3b1\u3bb\u3b5\u3c0\u3bf\u3cd"}'
awk 'BEGIN{print "cag\u308" "ed"}'
## Replace a specific occurrence
s='apple:banana:cherry:fig:mango'
echo "$s" | awk '{print gensub(/:/, "-", 2)}'
echo "$s" | awk '{print gensub(/[^:]+/, "123", 3)}'
echo '1 good 2 apples' | awk '{$4 = gensub(/[aeiou]/, "X", "g", $4)} 1'
## Backreferences
s='\[\] and \\w and \[a-zA-Z0-9\_\]'
echo "$s" | awk '{print gensub(/(\\?)\\/, "\\1", "g")}'
echo 'one,2,3.14,42' | awk '{print gensub(/^([^,]+).*/, "&,\\1", 1)}'
echo 'hello world' | awk '{sub(/.*/, "Hi. &. Have a nice day")} 1'
s='car,art,pot,tap,urn,ray,ear'
echo "$s" | awk '{print gensub(/(.*),((.*,){2})/, "\\1[]\\2", 1)}'
s='effort flee facade oddball rat tool'
echo "$s" | awk '{print gensub(/\w*(\w)\1\w*/, "X", "g")}'
echo "$s" | sed -E 's/\w*(\w)\1\w*/X/g'
s='one,2,3.14,42'
echo "$s" | awk '{$0=gensub(/^(([^,]+,){2})([^,]+)/, "[\\1](\\3)", 1)} 1'
s='tryst,fun,glyph,pity,why,group'
echo "$s" | awk '{print gensub(/\<\w+\>|(\<[gp]\w*y\w*\>)/, "\\1", "g")}'
echo "$s" | awk '{print gensub(/(\<[gp]\w*y\w*\>)|\<\w+\>/, "\\1", "g")}'
echo 'apple and fig' | awk '{sub(/and/, "[&]")} 1'
echo 'apple and fig' | awk '{sub(/and/, "[\\&]")} 1'
echo 'apple and fig' | awk '{sub(/and/, "\\")} 1'
## Case insensitive matching
printf 'Cat\ncOnCaT\nscatter\ncot\n' | awk -v IGNORECASE=1 '/cat/'
printf 'Cat\ncOnCaT\nscatter\ncot\n' | awk '{gsub(/[cC][aA][tT]/, "(&)")} 1'
printf 'Cat\ncOnCaT\nscatter\ncot\n' | awk 'tolower($0) ~ /cat/'
## Dynamic regexp
r='cat.*dog|dog.*cat'
echo 'two cats and a dog' | awk -v ip="$r" '{gsub(ip, "pets")} 1'
awk -v s='ow' '$0 ~ s' table.txt
r='\\<[12][0-9]\\>'
echo '23 154 12 26 34' | awk -v ip="$r" '{gsub(ip, "X")} 1'
awk -v s='(a.b)^{c}|d' 'BEGIN{gsub(/[{[(^$*?+.|\\]/, "\\\\&", s); print s}'
echo 'f*(a^b) - 3*(a^b)' |
awk -v s='(a^b)' '{gsub(/[{[(^$*?+.|\\]/, "\\\\&", s); gsub(s, "c")} 1'
echo 'f*(a^b) - 3*(a^b)' |
awk -v s='(a^b)' '{gsub(/[{[(^$*?+.|\\]/, "\\\\&", s); gsub(s "$", "c")} 1'
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