Awk
useful
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 } '
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