Shell Programming and Scripting

Would you please tell me any link to learn about the concepts of coprocess from teh start and tell me briefly its applications, ie when, where, why to use co-process, and ive seen its applied to much in an ftp script. why its importnat in an ftp script

ill appreciata hihly your help. Thanks

deleted - redundent

I really hate to say it, but:

@porter: please do not answer to threads where you have obviously not the slightest idea of what is being spoken about.

Coprocesses are a device in the Korn Shell with which a background process can be started but (unlike usual background processes) communication between the father- and the child-process is being maintained.

By default coprocesses communicate via I/O-channel 4 and 5 with the father process. That means if a coprocess sends something to its <stdout> it can be in the father process by reading from channel 4 and writing to channel 5 in the father process appear in <stdin> of the child process.

The reason why this is valuable for scripts using ftp is because ftp is designed as an interactive program and not very well suited for batch operation. Hence one can start the ftp-process as coprocess and process the output and provide the input within the father process, quasi-simulating an interactive ftp-session.

Get yourself a good Korn Shell book (I'd strongly recommend Barry Rosenbergs "Hands-on Kornshell93 programming", very informative AND funny to read) to find about about the coprocess facility in ksh.

bakunin