Basic syntax
awk [ options ] script filename
Where script is either a single awk command or file of awk commands. Awk commands look like this:
TODO
and filename can be omitted if you’re piping in standard input.
Commands
Options
Examples
Length of the longest line in a file
awk '{ if (length($0) > max) max = length($0) }; END { print max }' file
Selecting, filtering, and basic arithmetic
Sum a field, specify delimiter
awk -F '\t' '{print sum+=$1;} END {print sum}' file.txt
will print the sum of column one ($1) of a tab-separated (\t) file (file.txt).
awk -F ',' '$1 ~ /smiths/ {sum += $3} END {print sum}' file.txt
sums values in column three where column 1 equals smiths in a comma-separated file.
Using named columns is a bit more difficult. The following snippet lets you do that. Just replace the second command ({print $(f["foo"])... with the command you wish to execute. I haven’t tried this with large files, but I imagine it can get slow.
awk 'NR==1 {for (i=1; i<=NF; i++) {f[$i] = i}} {print $(f["foo"]), $(f["baz"])}' file
String substitution
Replace all instances of "-" in column 54 of a comma-separated file and print new file to stdout:
awk '{ FS=","; OFS=","; gsub("-", "", $54); print }' file.csv > new_file.csv