C figure 828 signal1 this program is awed because it

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: task is to call the parseline function (Figure 8.22), which parses the space-separated command-line arguments and builds the argv vector that will eventually be passed to execve. The first argument is assumed to be either the name of a built-in shell command that is interpreted immediately, or an executable object file that will be loaded and run in the context of a new child process. If the last argument is a “&” character, then parseline returns 1, indicating that the program should be executed in the background (the shell does not wait for it to complete). Otherwise it returns 0, indicating that the program should be run in the foreground (the shell waits for it to complete). After parsing the command line, the eval function calls the builtin command function, which checks whether the first command line argument is a built-in shell command. If so, it interprets the command immediately and returns 1. Otherwise, it returns 0. Our simple shell has just one built-in command, the quit command, which terminates the shell. Real shells have numerous commands, such as pwd, jobs, and fg. If builtin...
View Full Document

This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.

Ask a homework question - tutors are online