Programming Perl, 4th Edition

exec

exec PATHNAME LIST
exec LIST

The exec function terminates the current program and executes an external command and never returns!!! Use system instead of exec to return to your program after the commands complete. The exec function fails and returns false only if the command does not exist and if it is executed directly instead of via your system’s command shell, discussed below.

If there is only one scalar argument, the argument is checked for shell metacharacters. If metacharacters are found, the entire argument is passed to the system’s standard command interpreter (/bin/sh under Unix). If there are no metacharacters, the argument is split into words and executed directly, since in the interests of efficiency this bypasses the overhead of shell processing. It also gives you more control of error recovery should the program not exist.

If there is more than one argument in LIST, or if LIST is an array with more than one value, the system shell will never be used. This also bypasses any shell processing of the command. The presence or absence of metacharacters in the arguments doesn’t affect this list-triggered behavior, which makes it the preferred form in security-conscious programs that do not wish to expose themselves to injection attacks via shell escapes.

This example causes ...