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Full Discussion: How does ||: evaluate?
Top Forums UNIX for Dummies Questions & Answers How does ||: evaluate? Post 302755085 by Don Cragun on Friday 11th of January 2013 06:48:01 PM
Old 01-11-2013
Quote:
Originally Posted by jim mcnamara
: evaluates in POSIX shells to the result of /usr/bin/true or true.

It is used like that to override a return status value that would affect subsequent processing.

For example, in Appworx (a batch control system) a false return code almost anywhere is detectable, so that if ||: were not there at the end of a line, appworx may see a false return and abort the job when the child process returns. Even though the job may have completed correctly.

Don't ask how, I'd have to guess.
A likely way to make this happen would be to use the command:
set -e
in a script that Appworx uses to start jobs, or for Appworx to use sh -e when it invokes a shell script.
 

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qmsg(1B)								PBS								  qmsg(1B)

NAME
qmsg - send message to pbs batch jobs SYNOPSIS
qmsg [-E] [-O] message_string job_identifier ... DESCRIPTION
To send a message to a job is to write a message string into one or more output files of the job. Typically this is done to leave an informative message in the output of the job. The qmsg command writes messages into the files of jobs by sending a Message Job batch request to the batch server that owns the job. The qmsg command does not directly write the message into the files of the job. OPTIONS
-E Specifies that the message is written to the standard error of each job. -O Specifies that the message is written to the standard output of each job. If neither the -E nor the -O option is specified, the message will be written to the standard error of the job. OPERANDS
The first operand, message_string, is the message to be written. If the string contains blanks, the string must be quoted. If the final character of the string is not a newline, a newline character will be added when written to the job's file. All following operands are job_identifiers which specify the jobs to receive the message string. The qmsg command accepts one or more job_identifier operands of the form: sequence_number[.server_name][@server] STANDARD ERROR
The qmsg command will write a diagnostic message to standard error for each error occurrence. EXIT STATUS
Upon successful processing of all the operands presented to the qmsg command, the exit status will be a value of zero. If the qmsg command fails to process any operand, the command exits with a value greater than zero. SEE ALSO
qsub(1B), pbs_msgjob(3B) Local qmsg(1B)
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