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HP OpenVMS Systemsask the wizard |
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The Question is: Hello. After searching through previous questions sent to you and the FAQ's I could find nothing to answer my question. So here goes. On one line, we need to be able to run an executable in DCL and have the output redirected to the null device (nl:). This command is going to be called from within a C++ program using the system() function. We want to redirect the output to NULL because we do not need to see it. All we need to do is verify that it runs correctly and returns a good exit status. For the UNIX machines the lines would be like this: string = /directory/exe -option > /dev/null system(string); The reason we need a one liner is because our C++ program runs on multiple platforms, one being VMS, another being UNIX. Therefore, we would like to keep the platform specific code down to a minimum. I know what we want to do can be accomplished with a command file such as: $ define SYS$OUTPUT nl: $ /directory/exe -option $ deassign SYS$OUTPUT However, we want to avoid having to dynamically generate this file from the C++ program and having to an pass argument to it. In other words, there is a lot of VMS specific code. We also know that we can possibly accomplish this using LIB$SPAWN but this will cause us to generate a lot of VMS specific code also. I know in V 7.1 there is a new DCL command PIPE. However, we are running V 6.2. So, on one line, is there any way to run a command and redirect it's output to nl:? If not, is there a way to enter multiple commands on one DCL line, i.e. $ define SYS$OUTPUT nl: ; /directory/exe /option ; deassign SYS$OUTPUT Thanks in advance. The Answer is : The Wizard recommends the use of the LIB$SPAWN routine, rather than the C system call. The C system call is implemented using the LIB$SPAWN so the effect is the same, save that LIB$SPAWN allows you to explicitly specify the input, output, and error devices. Obviously, specify the output and error parameters as the NLA0: device. This code can be easily conditionalized within an #ifdef/#endif block. Other alternatives would include rather more OpenVMS-specific code, such as using a mailbox or other OpenVMS device.
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