3.4. Handling Errors from System Calls and Library Functions

Almost every system call and library function returns some type of status value indicating whether the call succeeded or failed. This status value should always be checked to see whether the call succeeded. If it did not, then appropriate action should be taken—at the very least, the program should display an error message warning that something unexpected occurred.

Although it is tempting to save typing time by excluding these checks (especially after seeing examples of UNIX and Linux programs where status values are not checked), it is a false economy. Many hours of debugging time can be wasted because a check was not made on the status return of a system call or library function that “couldn’t possibly fail.”