Awk

basic

The following simple commands are used most often.

awk 'pattern' file   # print lines matching pattern
awk '{action}' file  # take action for every line
awk 'pattern {action}' file

$0, $1, $2,... 	Field variables
FILENAME 	Name of input file
FS 	Field separator, by default the space character. Can be modified.
NF 	Number of fields in the current record
NR 	Number of the current record (line number)
OFMT 	Output format (default: "%.6g")
RS	Record Separator
ORS	Output Record Separator. By default, the output and input records separators are a carriage return stored in the built-in variables ORS and RS, respectively.

print every 5 line

awk 'NR % 5 == 0'

awk script

awk 'BEGIN           {initializations}
     search_pattern1 {actions}
     search_pattern2 {actions}
     ...
     END             {final actions}'  file

useful

Remove 2 first lines of file.

awk 'NR > 2' /tmp/tmp

Get media information. Pick encoded date, replace : with -, print row 6 and 7 and add .mov. Find just once.

mediainfo *.mov | awk '/Encoded date/ { gsub(/:/,"-") ; print $6 "_" $7 ".mov" ;exit }'

awk with replace

Replace systemd with andreas and print column 1.

awk -F: '{gsub ("systemd","andreas")}{print $1}' /etc/passwd

Move last column to first

| awk '{ print $NF, $0 }' | sed 's/[^ ]*$//g'

remove xml comments

 awk -v RS='<!--|-->' 'NR%2' file

remove column 6 and 8.

awk '{$6=$8=""; print $0}' file

print something between tags

 
awk -F'[<|>]' '/jndi/{print $3}'

print lines containing both cat, dog and bird.

awk '/cat/ && /dog/ && /bird/' files

Print rows where first column doesnt contains ABC

awk '$1 !~ /ABC/' file # print lines whose 1st field doesn't

Print lines where 8 column does not contain a date

awk -F',' '$8 !~ /[0-9]{4,}/' list.csv

Print row 5 and 9.

awk 'NR==5 || NR==9' "file"

Print row betwen 5 and 9.

awk 'NR>=5&&NR<=9' "file"

Print column 4 to the end of passwd. Field separator set to :

cat /etc/passwd | awk ' BEGIN { FS=":" } {
for (i=4; i<=NF; i++)
printf("%s ", $i)
printf("\n") # CR at end of line
} '

Summarize size of files.

find . -type f -printf '%s\n' | awk '{ a+=$1 } END { print a }'

Summarize on 5 column. MB

awk '{ SUM +=  $5} END { print SUM/1024/1024 }' 

Summarize on 5 column. GB

awk '{ SUM +=  $5} END { print SUM/1024/1024/1024 }'

Print lines containing T2 in second column.

awk '$2 ~ /T2/' file

Print second column where 1 columnt contains nodev

awk '$1 == "nodev" { print $2 }'

Print lines where first column value is bigger than 10

awk '$1 > 10'

lenght

Print length of string.

awk '{ print length(), $0 }'

Print fields matching regexp in 5 column delimiter being ,

awk -F',' '$5 ~ /^10.[0-9]*.21.[0-9]*/'

Print lines where 4 column is empty

awk 'BEGIN {FS=","} $4=="" {print}'

awk one liners

FILE SPACING:

# 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 (\r\n) 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”}’

NUMBERING AND CALCULATIONS:

# precede each line by its line number FOR THAT FILE (left alignment).
# Using a tab (\t) 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*

# 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 \r (mentioned above)
awk ‘NF{$0=++a ” :” $0};{print}’
awk ‘{print (NF? ++a ” :” :”") $0}’

# count lines (emulates “wc -l”)
awk ‘END{print NR}’

# print the sums of the fields of every line
awk ‘{s=0; for (i=1; i 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 the last field of the last line
awk ‘{ field = $NF }; END{ print field }’

# 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′

TEXT CONVERSION AND SUBSTITUTION:


# IN UNIX ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format
awk ‘{sub(/\r$/,”");print}’ # assumes EACH line ends with Ctrl-M

# IN UNIX ENVIRONMENT: convert Unix newlines (LF) to DOS format
awk ‘{sub(/$/,”\r”);print}

# 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

# Use “tr” instead.
tr -d \r outfile # GNU tr version 1.22 or higher

# delete leading whitespace (spaces, tabs) from front of each line
# aligns all text flush left
awk ‘{sub(/^[ \t]+/, “”); print}’

# delete trailing whitespace (spaces, tabs) from end of each line
awk ‘{sub(/[ \t]+$/, “”);print}’

# delete BOTH leading and trailing whitespace from each line
awk ‘{gsub(/^[ \t]+|[ \t]+$/,”");print}’
awk ‘{$1=$1;print}’ # also removes extra space between fields

# insert 5 blank spaces at beginning of each line (make page offset)
awk ‘{sub(/^/, ” “);print}’

# 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”);print}’ # replaces only 1st instance
gawk ‘{$0=gensub(/foo/,”bar”,4);print}’ # replaces only 4th instance
awk ‘{gsub(/foo/,”bar”);print}’ # replaces ALL instances in a line

# substitute “foo” with “bar” ONLY for lines which contain “baz”
awk ‘/baz/{gsub(/foo/, “bar”)};{print}’

# substitute “foo” with “bar” EXCEPT for lines which contain “baz”
awk ‘!/baz/{gsub(/foo/, “bar”)};{print}’

# change “scarlet” or “ruby” or “puce” to “red”
awk ‘{gsub(/scarlet|ruby|puce/, “red”); print}’

# 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);printf (”\n”)}’ file

# 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

# concatenate every 5 lines of input, using a comma separator
# between fields
awk ‘ORS=%NR%5?”,”:”\n”‘ file

SELECTIVE PRINTING OF CERTAIN LINES:

# print first 10 lines of file (emulates behavior of “head”)
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 the line immediately before a regex, but not the line
# containing the regex
awk ‘/regex/{print x};{x=$0}’
awk ‘/regex/{print (x==”" ? “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)
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

# 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


SELECTIVE DELETION OF CERTAIN LINES:

 # delete ALL blank lines from a file (same as "grep '.' ")
 awk NF
 awk '/./'

run command on mathed pattern

ls -la | awk '/^drwx/ { system("echo directory with certain permissions" $NF) }'