HANDY
ONE-LINERS FOR AWK 22 July
2003 |
compiled by Eric Pement
version 0.22 |
Latest version of this file is usually at: |
http://www.student.northpark.edu/pemente/awk/awk1line.txt |
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USAGE: |
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Unix:
awk '/pattern/ {print "$1"}' # standard Unix shells |
DOS/Win:
awk '/pattern/ {print "$1"}' # okay for DJGPP compiled |
awk "/pattern/ {print
\"$1\"}" # required for
Mingw32 |
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Most of my experience comes
from version of GNU awk (gawk) compiled for |
Win32. Note in particular that
DJGPP compilations permit the awk script |
to follow Unix quoting syntax
'/like/ {"this"}'. However, the user must |
know that single quotes under
DOS/Windows do not protect the redirection |
arrows (<, >) nor do
they protect pipes (|). Both are special symbols |
for the DOS/CMD command shell
and their special meaning is ignored only |
if they are placed within
"double quotes." Likewise, DOS/Win users must |
remember that the percent sign
(%) is used to mark DOS/Win environment |
variables, so it must be
doubled (%%) to yield a single percent sign |
visible to awk. |
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If I am sure that a script
will NOT need to be quoted in Unix, DOS, or |
CMD, then I normally omit the
quote marks. If an example is peculiar to |
GNU awk, the command 'gawk'
will be used. Please notify me if you find |
errors or new commands to add
to this list (total length under 65 |
characters). I usually try to
put the shortest script first. |
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FILE SPACING: |
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# double space a file |
awk '1;{print ""}' |
awk 'BEGIN{ORS="\n\n"};1' |
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# 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"}' |
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# triple space a file |
awk '1;{print "\n"}' |
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NUMBERING AND CALCULATIONS: |
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# 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* |
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# precede each line by its line number FOR
ALL FILES TOGETHER, with tab. |
awk '{print NR "\t" $0}' files* |
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# 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)}' |
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# 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 " :"
:"") $0}' |
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# count lines (emulates "wc -l") |
awk 'END{print NR}' |
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# print the sums of the fields of every line |
awk '{s=0; for (i=1; i<=NF; i++) s=s+$i;
print s}' |
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# add all fields in all lines and print the
sum |
awk '{for (i=1; i<=NF; i++) s=s+$i};
END{print s}' |
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# print every line after replacing each
field with its absolute value |
awk '{for (i=1; i<=NF; i++) if ($i <
0) $i = -$i; print }' |
awk '{for (i=1; i<=NF; i++) $i = ($i <
0) ? -$i : $i; print }' |
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# print the total number of fields
("words") in all lines |
awk '{ total = total + NF }; END {print
total}' file |
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# print the total number of lines that
contain "Beth" |
awk '/Beth/{n++}; END {print n+0}' file |
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# 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}' |
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# print the number of fields in each line,
followed by the line |
awk '{ print NF ":" $0 } ' |
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# print the last field of each line |
awk '{ print $NF }' |
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# print the last field of the last line |
awk '{ field = $NF }; END{ print field }' |
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# print every line with more than 4 fields |
awk 'NF > 4' |
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# print every line where the value of the
last field is > 4 |
awk '$NF > 4' |
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TEXT CONVERSION AND
SUBSTITUTION: |
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# IN UNIX ENVIRONMENT: convert DOS newlines
(CR/LF) to Unix format |
awk '{sub(/\r$/,"");print}' # assumes EACH line ends with Ctrl-M |
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# IN UNIX ENVIRONMENT: convert Unix newlines
(LF) to DOS format |
awk '{sub(/$/,"\r");print} |
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# IN DOS ENVIRONMENT: convert Unix newlines
(LF) to DOS format |
awk 1 |
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# 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 |
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# Use "tr" instead. |
tr -d \r outfile # GNU tr version 1.22 or higher |
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# delete leading whitespace (spaces, tabs)
from front of each line |
# aligns all text flush left |
awk '{sub(/^[ \t]+/, ""); print}' |
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# delete trailing whitespace (spaces, tabs)
from end of each line |
awk '{sub(/[ \t]+$/, "");print}' |
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# delete BOTH leading and trailing
whitespace from each line |
awk '{gsub(/^[ \t]+|[
\t]+$/,"");print}' |
awk '{$1=$1;print}' # also removes extra space between
fields |
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# insert 5 blank spaces at beginning of each
line (make page offset) |
awk '{sub(/^/, " ");print}' |
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# align all text flush right on a 79-column
width |
awk '{printf "%79s\n", $0}' file* |
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# center all text on a 79-character width |
awk '{l=length();s=int((79-l)/2); printf
"%"(s+l)"s\n",$0}' file* |
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# 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 |
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# substitute "foo" with
"bar" ONLY for lines which contain "baz" |
awk '/baz/{gsub(/foo/,
"bar")};{print}' |
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# substitute "foo" with
"bar" EXCEPT for lines which contain "baz" |
awk '!/baz/{gsub(/foo/,
"bar")};{print}' |
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# change "scarlet" or
"ruby" or "puce" to "red" |
awk '{gsub(/scarlet|ruby|puce/,
"red"); print}' |
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# reverse order of lines (emulates
"tac") |
awk '{a[i++]=$0} END {for (j=i-1; j>=0;)
print a[j--] }' file* |
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# if a line ends with a backslash, append
the next line to it |
# (fails if there are multiple lines ending
with backslash...) |
awk '/\\$/ {sub(/\\$/,""); getline
t; print $0 t; next}; 1' file* |
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# print and sort the login names of all
users |
awk -F ":" '{ print $1 |
"sort" }' /etc/passwd |
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# print the first 2 fields, in opposite
order, of every line |
awk '{print $2, $1}' file |
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# switch the first 2 fields of every line |
awk '{temp = $1; $1 = $2; $2 = temp}' file |
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# print every line, deleting the second
field of that line |
awk '{ $2 = ""; print }' |
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# print in reverse order the fields of every
line |
awk '{for (i=NF; i>0; i--)
printf("%s ",i);printf ("\n")}' file |
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# remove duplicate, consecutive lines
(emulates "uniq") |
awk 'a !~ $0; {a=$0}' |
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# remove duplicate, nonconsecutive lines |
awk '! a[$0]++' # most concise script |
awk '!($0 in a) {a[$0];print}' # most efficient script |
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# concatenate every 5 lines of input, using
a comma separator |
# between fields |
awk 'ORS=%NR%5?",":"\n"'
file |
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SELECTIVE PRINTING OF CERTAIN
LINES: |
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# print first 10 lines of file (emulates
behavior of "head") |
awk 'NR < 11' |
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# print first line of file (emulates
"head -1") |
awk 'NR>1{exit};1' |
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# print the last 2 lines of a file
(emulates "tail -2") |
awk '{y=x "\n" $0; x=$0};END{print
y}' |
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# print the last line of a file (emulates
"tail -1") |
awk 'END{print}' |
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# print only lines which match regular
expression (emulates "grep") |
awk '/regex/' |
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# print only lines which do NOT match regex
(emulates "grep -v") |
awk '!/regex/' |
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# 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}' |
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# print the line immediately after a regex,
but not the line |
# containing the regex |
awk '/regex/{getline;print}' |
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# grep for AAA and BBB and CCC (in any
order) |
awk '/AAA/; /BBB/; /CCC/' |
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# grep for AAA and BBB and CCC (in that
order) |
awk '/AAA.*BBB.*CCC/' |
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# print only lines of 65 characters or
longer |
awk 'length > 64' |
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# print only lines of less than 65
characters |
awk 'length < 64' |
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# print section of file from regular
expression to end of file |
awk '/regex/,0' |
awk '/regex/,EOF' |
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# print section of file based on line
numbers (lines 8-12, inclusive) |
awk 'NR==8,NR==12' |
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# print line number 52 |
awk 'NR==52' |
awk 'NR==52 {print;exit}' # more efficient on large files |
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# print section of file between two regular
expressions (inclusive) |
awk '/Iowa/,/Montana/' # case sensitive |
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SELECTIVE DELETION OF CERTAIN
LINES: |
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# delete ALL blank lines from a file (same
as "grep '.' ") |
awk NF |
awk '/./' |
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CREDITS AND THANKS: |