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# AWK

## Basics I

## Variables

## Functions

## OneLiners

Execute action for matched pattern ‘pattern’ on file ‘file’

  awk /pattern/ {action} file

Print first field for each record in file

  awk '{print $1}' file

Print only lines that match regex in file

  awk '/regex/' file

Print only lines that do not match regex in file

  awk '!/regex/' file

Print any line where field 2 is equal to “foo” in file

  awk '$2 == "foo"' file

Print lines where field 2 is NOT equal to “foo” in file

  awk '$2 != "foo"' file

Print line if field 1 matches regex in file

  awk '$1 ~ /regex/' file

Print line if field 1 does NOT match regex in file

  awk '$1 !~ /regex/' file

Print first field for each record in file excluding the first record

  awk 'NR!=1{print $1}' file

Count lines in file

  awk 'END{print NR}' file

Print total number of lines that contain foo

  awk '/foo/{n++}; END {print n+0}' file

Print total number of fields in all lines

  awk '{total=total+NF};END{print total}' file

Print line immediately after regex, but not line containing regex in file

  awk '/regex/{getline;print}' file

Print lines with more than 32 characters in file

  awk 'length > 32' file

Print line number 12 of file

  awk 'NR==12' file

Precede each line by its line number FOR THAT FILE (left alignment). Using a tab ( instead of space will preserve margins.

  awk '{print FNR "\t" $0}' files*

Precede each line by its line number FOR ALL FILES TOGETHER, with tab.

  awk '{print NR "\t" $0}' files*

Print diagram of user/groups

  awk 'BEGIN{FS=":"; print "digraph{"}{split($4, a, ",");for (i in a) printf "\"%s\" [shape=box];\n\"%s\" -> \"%s\";\n", $1, a[i], $1}END{print "}"}' /etc/group|display

print the sums of the fields of every line

  awk '{s=0; for (i=1; i<=NF; i++) s=s+$i; print s}'

add all fields in all lines and print the sum

  awk '{for (i=1; i<=NF; i++) s=s+$i}; END{print s}'

print every line after replacing each field with its absolute value

  awk '{for (i=1; i<=NF; i++) if ($i < 0) $i = -$i; print }'
  awk '{for (i=1; i<=NF; i++) $i = ($i < 0) ? -$i : $i; print }'

print the total number of fields (“words”) in all lines

  awk '{ total = total + NF }; END {print total}' file

print the total number of lines that contain “Beth”

  awk '/Beth/{n++}; END {print n+0}' file

print the largest first field and the line that contains it Intended for finding the longest string in field \#1

  awk '$1 > max {max=$1; maxline=$0}; END{ print max, maxline}'

print the number of fields in each line, followed by the line

  awk '{ print NF ":" $0 } '

print the last field of each line

  awk '{ print $NF }'

print every line with more than 4 fields

  awk 'NF > 4'

print every line where the value of the last field is \> 4

  awk '$NF > 4'

create a string of a specific length (e.g., generate 513 spaces)

  awk 'BEGIN{while (a++<513) s=s " "; print s}'

double space a file

  awk '1;{print ""}'
  awk 'BEGIN{ORS="\n\n"};1'

double space a file which already has blank lines in it. Output file should contain no more than one blank line between lines of text. NOTE: On Unix systems, DOS lines which have only CRLF () are often treated as non-blank, and thus ‘NF’ alone will return TRUE.

  awk 'NF{print $0 "\n"}'

triple space a file

  awk '1;{print "\n"}'

IN UNIX ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format

  awk '{sub(/\r$/,"")};1'   # assumes EACH line ends with Ctrl-M

IN UNIX ENVIRONMENT: convert Unix newlines (LF) to DOS format

  awk '{sub(/$/,"\r")};1'

IN DOS ENVIRONMENT: convert Unix newlines (LF) to DOS format

  awk 1

IN DOS ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format Cannot be done with DOS versions of awk, other than gawk

  gawk -v BINMODE="w" '1' infile >outfile

delete leading whitespace (spaces, tabs) from front of each line aligns all text flush left

  awk '{sub(/^[ \t]+/, "")};1'

delete trailing whitespace (spaces, tabs) from end of each line

  awk '{sub(/[ \t]+$/, "")};1'

delete BOTH leading and trailing whitespace from each line

  awk '{gsub(/^[ \t]+|[ \t]+$/,"")};1'
  awk '{$1=$1};1'           # also removes extra space between fields

insert 5 blank spaces at beginning of each line (make page offset)

``` awk '{sub(/^/, “ ”)};1'

```

align all text flush right on a 79-column width

  awk '{printf "%79s\n", $0}' file*

center all text on a 79-character width

  awk '{l=length();s=int((79-l)/2); printf "%"(s+l)"s\n",$0}' file*

substitute (find and replace) “foo” with “bar” on each line

  awk '{sub(/foo/,"bar")}; 1'           # replace only 1st instance
  gawk '{$0=gensub(/foo/,"bar",4)}; 1'  # replace only 4th instance
  awk '{gsub(/foo/,"bar")}; 1'          # replace ALL instances in a line

substitute “foo” with “bar” ONLY for lines which contain “baz”

  awk '/baz/{gsub(/foo/, "bar")}; 1'

substitute “foo” with “bar” EXCEPT for lines which contain “baz”

  awk '!/baz/{gsub(/foo/, "bar")}; 1'

change “scarlet” or “ruby” or “puce” to “red”

  awk '{gsub(/scarlet|ruby|puce/, "red")}; 1'

reverse order of lines (emulates “tac”)

  awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }' file*

if a line ends with a backslash, append the next line to it (fails if there are multiple lines ending with backslash…)

  awk '/\\$/ {sub(/\\$/,""); getline t; print $0 t; next}; 1' file*

print and sort the login names of all users

  awk -F ":" '{print $1 | "sort" }' /etc/passwd

print the first 2 fields, in opposite order, of every line

  awk '{print $2, $1}' file

switch the first 2 fields of every line

  awk '{temp = $1; $1 = $2; $2 = temp}' file

print every line, deleting the second field of that line

  awk '{ $2 = ""; print }'

print in reverse order the fields of every line

  awk '{for (i=NF; i>0; i--) printf("%s ",$i);print ""}' file

concatenate every 5 lines of input, using a comma separator between fields

  awk 'ORS=NR%5?",":"\n"' file

count lines (emulates “wc -l”)

  awk 'END{print NR}'

print first 10 lines of file (emulates behavior of “head”)

  awk 'NR < 11'

print first line of file (emulates “head -1”)

  awk 'NR>1{exit};1'

print the last 2 lines of a file (emulates “tail -2”)

  awk '{y=x "\n" $0; x=$0};END{print y}'

print the last line of a file (emulates “tail -1”)

  awk 'END{print}'

print only lines which match regular expression (emulates “grep”)

  awk '/regex/'

print only lines which do NOT match regex (emulates “grep -v”)

  awk '!/regex/'

print any line where field \#5 is equal to “abc123”

  awk '$5 == "abc123"'

print only those lines where field \#5 is NOT equal to “abc123” This will also print lines which have less than 5 fields.

  awk '$5 != "abc123"'
  awk '!($5 == "abc123")'

matching a field against a regular expression

  awk '$7  ~ /^[a-f]/'    # print line if field #7 matches regex
  awk '$7 !~ /^[a-f]/'    # print line if field #7 does NOT match regex

print the line immediately before a regex, but not the line containing the regex

  awk '/regex/{print x};{x=$0}'
  awk '/regex/{print (NR==1 ? "match on line 1" : x)};{x=$0}'

print the line immediately after a regex, but not the line containing the regex

  awk '/regex/{getline;print}'

grep for AAA and BBB and CCC (in any order on the same line)

  awk '/AAA/ && /BBB/ && /CCC/'

grep for AAA and BBB and CCC (in that order)

  awk '/AAA.*BBB.*CCC/'

print only lines of 65 characters or longer

  awk 'length > 64'

print only lines of less than 65 characters

  awk 'length < 64'

print section of file from regular expression to end of file

  awk '/regex/,0'
  awk '/regex/,EOF'

print section of file based on line numbers (lines 8-12, inclusive)

  awk 'NR==8,NR==12'

print line number 52

  awk 'NR==52'
  awk 'NR==52 {print;exit}'          # more efficient on large files

print section of file between two regular expressions (inclusive)

  awk '/Iowa/,/Montana/'             # case sensitive

delete ALL blank lines from a file (same as “grep ‘.’”)

  awk NF
  awk '/./'

remove duplicate, consecutive lines (emulates “uniq”)

  awk 'a !~ $0; {a=$0}'

remove duplicate, nonconsecutive lines

  awk '!a[$0]++'                     # most concise script
  awk '!($0 in a){a[$0];print}'      # most efficient script

number each line of a file (number on left, right-aligned) Double the percent signs if typing from the DOS command prompt.

  awk '{printf("%5d : %s\n", NR,$0)}'

number each line of file, but only print numbers if line is not blank Remember caveats about Unix treatment of mentioned above)

  awk 'NF{$0=++a " :" $0};1'
  awk '{print (NF? ++a " :" :"") $0}'

## Filtrar columnas

Sirve para filtrar por columnas en una cadena de texto:


## IMPRIMIR ÚLTIMA COLUMNA

Si queremos imprimir la última columna con awk, utilizaríamos $NF:


Otro ejemplo de cómo imprimir la última columna con awk:


CONECTAR COLUMNAS También podemos conectar unas columnas con otras de la siguiente forma, por ejemplo agregando flechas:


## ESTABLECER UN DELIMITADOR

También podemos establecer un delimitador para que nos cuente a partir de un determinado patrón, por ejemplo de un punto:


Otro ejemplo: