... have read about line addressing only, and just one command was dis-played, which is the command l for print. oa` has many other commands as well, of which the o (substitute) command is without ... first two lines from this file, you can use the oa` com-mand .m. With this command, you tell oa` to show two lines, and then quit (m). Listing 4-15 shows the results of this command. Listing ... automate commands on text files. To do this, oa` processes the text file line by line to see whether a command has to be executed on these lines. By default, oa` will write its result to standard...