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"}'
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};1'
awk '{print (NF? ++a " :" :"") $0}'
count lines (emulates "wc -l")
awk 'END{print NR}'
print the sums of the fields of every line
awk '{s=0; for (i=1; i<=NF; i++) s=s+$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 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'
create a string of a specific length (e.g., generate 513 spaces)
awk 'BEGIN{while (a++<513) s=s " "; print s}'
insert a string of specific length at a certain character position
Example: insert 49 spaces after column #6 of each input line.
gawk --re-interval 'BEGIN{while(a++<49)s=s " "};{sub(/^.{6}/,"&" s)};1'
These next 2 entries are not one-line scripts, but the technique
is so handy that it merits inclusion here.
create an array named "month", indexed by numbers, so that month[1]
is 'Jan', month[2] is 'Feb', month[3] is 'Mar' and so on.
split("Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec", month, " ")
create an array named "mdigit", indexed by strings, so that
mdigit["Jan"] is 1, mdigit["Feb"] is 2, etc. Requires "month" array
for (i=1; i<=12; i++) mdigit[month[i]] = i
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
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]+/, "")};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
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