If you do not specify a data file on the command line, awk begins to read data from standard input. For example, if you enter the command:

awk '{ print $1 }'

awk prints the first word of every line you type. When you type in data from the workstation, press <Enter> at the end of each line. To stop passing data to awk, type <EscChar-D> and press <Enter>.

A command line may also specify several data files, as in:

awk -f progfile data1 data2 data3 ...

When awk has finished reading through the first data file data1, it goes on to data2, and so on.