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Last update: 1997-05-20
9945-2-99 _____________________________________________________________________________ Topic: set -x Relevant Sections: 3.14.11 Defect Report: ----------------------- From: [email protected] (Andrew Josey) Date: Thu, 16 Mar 1995 07:32:02 +0000 This is an interpretation request for ISO/IEC 9945-2:1993. Topic : shell , set -x Publication: 9945-2:1993 POSIX.2 requires that "set -x" will write a trace for each command after the shell expands the command and before it executes it. The following script indicates that execution occurs before the trace is written, as the call to "set +x" is not recorded: set -x VAR1=1 VAR2=2 set +x VAR3=3 This behaviour is different to present Korn Shell, which has historically treated set +x specially; not tracing this. Several tools uses this to do selective tracing. We see that the standard doesn't specify a special case for this, but we know that it will break existing practice if we change this behavior. All other commands are traced before execution. Did the standard really intend to mandate the Bourne Shell behavior over Korn Shell, or was it just an oversight that they did not single out set +x as a special case? Interpretation response ------------------------ The standard clearly states the behavior of set +x, and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor. Rationale: None Forwarded to Interpretations group: Mar 16 1995 Proposed resolution circulated: May 16th Comments due: June 15th Finalised: June 16th 1995