gawk: add GNU version of awk

pages/common/awk.md

@@ -1,6 +1,8 @@
 # awk
 
 > A versatile programming language for working on files.
+> Note: Different implementations of AWK often make this a symlink of their binary.
+> See also: `gawk`.
 > More information: <https://github.com/onetrueawk/awk>.
 
 - Print the fifth column (a.k.a. field) in a space-separated file:

pages/common/gawk.md

@@ -0,0 +1,37 @@
+# gawk
+
+> GNU version of awk, a versatile programming language for working on files.
+> See also: `awk`.
+> More information: <https://www.gnu.org/software/gawk/manual/gawk.html>.
+
+- Print the fifth column (a.k.a. field) in a space-separated file:
+
+`gawk '{print $5}' {{path/to/file}}`
+
+- Print the second column of the lines containing "foo" in a space-separated file:
+
+`gawk '/{{foo}}/ {print $2}' {{path/to/file}}`
+
+- Print the last column of each line in a file, using a comma (instead of space) as a field separator:
+
+`gawk {{[-F|--field-separator]}} ',' '{print $NF}' {{path/to/file}}`
+
+- Sum the values in the first column of a file and print the total:
+
+`gawk '{s+=$1} END {print s}' {{path/to/file}}`
+
+- Print every third line starting from the first line:
+
+`gawk 'NR%3==1' {{path/to/file}}`
+
+- Print different values based on conditions:
+
+`gawk '{if ($1 == "foo") print "Exact match foo"; else if ($1 ~ "bar") print "Partial match bar"; else print "Baz"}' {{path/to/file}}`
+
+- Print all the lines which the 10th column value is between a min and a max:
+
+`gawk '($10 >= {{min_value}} && $10 <= {{max_value}})'`
+
+- Print table of users with UID >=1000 with header and formatted output, using colon as separator (`%-20s` mean: 20 left-align string characters, `%6s` means: 6 right-align string characters):
+
+`gawk 'BEGIN {FS=":";printf "%-20s %6s %25s\n", "Name", "UID", "Shell"} $4 >= 1000 {printf "%-20s %6d %25s\n", $1, $4, $7}' /etc/passwd`