The AWK utility can be invoked from the command line with various options to modify its behavior. Here are some common options that can be used with AWK:
– `-F`: Specifies the field separator used in the input file. By default, AWK uses whitespace as the field separator, but this can be changed using the `-F` option. For example, to specify a comma as the field separator, you can use `-F’,’`.
– `-f`: Specifies a file containing an AWK program to be executed. This is useful for running complex or multi-line AWK programs that are stored in a separate file. For example, to run an AWK program stored in the file `program.awk`, you can use `-f program.awk`.
– `-v`: Defines a variable and sets its value from the command line. For example, to define a variable `n` with a value of `10`, you can use `-v n=10`.
– `-i`: Modifies the input file in place. This option is only available in some versions of AWK, such as GNU AWK (`gawk`). It allows you to edit the input file directly, without having to redirect the output to a separate file.
– `-W`: Enables certain warnings or options. For example, `-Wposix` enables POSIX-compliant behavior, while `-Wtraditional` enables compatibility with traditional AWK behavior.
Here are some examples of using AWK with command-line options:
– To printthe second field of a comma-separated file, you can use the `-F` option to specify the field separator:
`
awk -F',' '{ print $2 }' file.csv
– To define a variable `n` and pass it to an AWK program stored in a separate file, you can use the `-v` and `-f` options together:
` awk -v n=10 -f program.awk file.txt
– To modify the input file in place to replace all occurrences of the word “foo” with “bar”, you can use the `-i` option (if available) along with the `gsub()` function:
`
gawk -i inplace '{ gsub(/foo/, "bar"); print }' file.txt
– To enable POSIX-compliant behavior, you can use the `-Wposix` option:
`
awk -Wposix '{ print toupper($0) }' file.txt