2.4 Naming Standard Input

Often, you may wish to read standard input together with other files. For example, you may wish to read one file, read standard input coming from a pipe, and then read another file.

The way to name the standard input, with all versions of awk, is to use a single, standalone minus sign or dash, ‘-’. For example:

some_command | awk -f myprog.awk file1 - file2

Here, awk first reads file1, then it reads the output of some_command, and finally it reads file2.

You may also use "-" to name standard input when reading files with getline (see Using getline from a File). And, you can even use "-" with the -f option to read program source code from standard input (see Command-Line Options).

In addition, gawk allows you to specify the special file name /dev/stdin, both on the command line and with getline. Some other versions of awk also support this, but it is not standard. (Some operating systems provide a /dev/stdin file in the filesystem; however, gawk always processes this file name itself.)