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Shell Programming and Scripting
Conditional delete -- New glitch
Post 303024214 by Don Cragun on Wednesday 3rd of October 2018 08:16:03 AM
10-03-2018
Quote:
But, commands in a compound list surrounded by braces are executed in the current process environment. But the order in which commands are executed in a pipeline isn't as clearly specified. If the cd in the compound list is executed before the sh at the end of the pipeline is invoked, the pipeline as written would work. If the cd in the compound list is executed after the sh at the end of the pipeline is invoked, the pipeline as written would fail with the diagnostic messages the submitter stated. Therefore, the code you showed us in post #1 has a race condition that may work sometimes and fail at other times. Your choice of shells might alter the likelihood of success or failure, but the race condition would always be there.
By putting the cd before the pipeline in an AND list, we are forcing it to be completed successfully before the pipeline is started; therefore, we know that all elements of the pipeline have to be executed in the desired working directory
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LEARN ABOUT SUSE
rmf
RMF(1) [nmh-1.5] RMF(1) NAME
rmf - remove an nmh folder SYNOPSIS
rmf [+folder] [-interactive | -nointeractive] [-version] [-help] DESCRIPTION
Rmf removes all of the messages (files) within the specified (or default) folder, and then removes the folder (directory) itself. If there are any files within the folder which are not a part of nmh, they will not be removed, and an error will be produced. If the folder is given explicitly or the -nointeractive option is given, then the folder will be removed without confirmation. Otherwise, the user will be asked for confirmation. If rmf can't find the current folder, for some reason, the folder to be removed defaults to `+inbox' (unless overridden by user's profile entry "Inbox") with confirmation. If the folder being removed is a subfolder, the parent folder will become the new current folder, and rmf will produce a message telling the user this has happened. This provides an easy mechanism for selecting a set of messages, operating on the list, then removing the list and returning to the current folder from which the list was extracted. If rmf s used on a read-only folder, it will delete all the (private) sequences (i.e., "atr-seq-folder" entries) for this folder from your context without affecting the folder itself. Rmf irreversibly deletes messages that don't have other links, so use it with caution. FILES
$HOME/.mh_profile The user profile PROFILE COMPONENTS
Path: To determine the user's nmh directory Current-Folder: To find the default current folder Inbox: To find the default inbox SEE ALSO
rmm(1) DEFAULTS
`+folder' defaults to the current folder, usually with confirmation `-interactive' if +folder' not given, `-nointeractive' otherwise CONTEXT
Rmf will set the current folder to the parent folder if a subfolder is removed; or if the current folder is removed, it will make "inbox" current. Otherwise, it doesn't change the current folder or message. BUGS
Although intuitively one would suspect that rmf works recursively, it does not. Hence if you have a sub-folder within a folder, in order to rmf the parent, you must first rmf each of the children. MH.6.8 11 June 2012 RMF(1)