HP XP P9500 Storage - Manual (Page 23)

connect parent/child processes (with some exceptions). Named pipes are strictly unidirectional, even
on systems where anonymous pipes are bidirectional (full-duplex).
Using the PIPE function in UNIX Systems
A named pipe is a special file that is used to transfer data between unrelated processes. One or more
processes write to it, while another process reads from it. Named pipes are visible in the file system
and may be viewed with ls like any other file. (Named pipes are also called FIFOs.) Named pipes
may be used to pass data between unrelated processes, while normal (unnamed) pipes can only
connect parent/child processes. Named pipes are strictly unidirectional, even on systems where
anonymous pipes are bidirectional (full-duplex).
Data Exchange Pipe Function Details
FCU can carry out data transmission to a pipe file. A user application opens and reads this pipe file,
and a direct data transmission is attained between the application and FCU. There is no need for it
to be output as a file on an HDD.
A named-pipe name is specified in a parameter definition file as the output file name. PIPE=Yes
needs to be specified as an option. Under these conditions, FCU will open a pipe file with the specified
output file name, and will transmit data to it.
If the specified file exists as a standard UNIX file, FCU re-creates a pipe file using the same name
(the UNIX file is deleted). Since FCU only inputs data to a pipe, the FCU function needs to obtain the
data via a user application. If data remains in the pipe, FCU will stop and processing does not
progress to the next step. The FCU function has a built-in timer. If the application does not continue
receiving data, FCU will send an error message after a certain set time, and it will progress to the
next logical process.
NOTE:
This function is only supported for UNIX systems. It is not supported for Windows. It is supported for
mainframe to open-system data transfer only. This function requires an application program or a
utility program to receive data entries using a named pipe.
Pipe Function Time-Out Value
• FCU waits for a Read Data Entries status message. A time-out error will be reported if the TIME
OUT VALUE is not set appropriately. The TIME OUT VALUE should be set in the WAIT_TIME_VALUE
environment variable. The limits are 0~1440 seconds (0 = unlimited). The default value is 10
when the timeout value is undefined.
• The following examples illustrate the use of the WAIT_TIME_VALUE environment variable.
NOTE:
After setting the variable, log out and log in again to establish the variable’s value.
• Example 1: For C shell:
• Add setenv WAIT_TIME_VALUE 300 to the file .cshrc in the home directory.
• If .cshrc does not exist, create it and add the setenv line.
• Example 2: For non-C shell:
HP StorageWorks P9000 Data Exchange User Guide 23