[no description] http://git.sudomsg.com/mirror/zsh/atom/Test/B07emulate.ztst?h=declarednull 2021-04-10T22:56:39Z 2021-04-10T22:56:39Z brian m. carlson sandals@crustytoothpaste.net 2021-01-04T00:23:00Z urn:sha1:f7a417388c73e7cfefb8e93fa8beba193fb1dd1f zsh typically runs the final command in a pipeline in the main shell instead of a subshell. However, POSIX specifies that all commands in a pipeline run in a subshell, but permits zsh's behavior as an extension. The default /bin/sh implementations on various Linux distros and the BSDs always use a subshell for all components of a pipeline. Since zsh may be used as /bin/sh in some cases (such as macOS Catalina), it makes sense to have the common sh behavior when emulating sh, so do that by checking for being the final item of a multi-item pipeline and creating a subshell in that case. From the comment above execpline(), we know the following: last1 is a flag that this command is the last command in a shell that is about to exit, so we can exec instead of forking. It gets passed all the way down to execcmd() which actually makes the decision. A 0 is always passed if the command is not the last in the pipeline. […] If last1 is zero but the command is at the end of a pipeline, we pass 2 down to execcmd(). So there are three cases to consider in this code: • last1 is 0, which means we are not at the end of a pipeline, in which case we should not change behavior. • last1 is 1, which means we are effectively running in a subshell, because nothing that happens due to the exec is going to affect the actual shell, since it will have been replaced. So there is nothing to do here. • last1 is 2, which means our command is at the end of the pipeline, so in sh mode we should create a subshell by forking. input is nonzero if the input to this process is a pipe that we've opened. At the end of a multi-stage pipeline, it will necessarily be nonzero. Note that several of the tests may appear bizarre, since most developers do not place useless variable assignments directly at the end of a pipeline. However, as the function tests demonstrate, there are cases where assignments may occur when a shell function is used at the end of a command. The remaining assignment tests simply test additional cases, such as the use of local, that would otherwise be untested. 2017-09-11T09:12:17Z Peter Stephenson pws@zsh.org 2017-09-11T09:12:17Z urn:sha1:2ef3dff65a9fc0bc69446374473ad08e6fff4755 This sets the shell emulation mode similarly to ARGV0=... which doesn't work from other shells. Note that this gives more comprehensive emulation than running emulate within the shell. 2015-03-29T04:08:02Z Barton E. Schaefer schaefer@zsh.org 2015-03-29T04:08:02Z urn:sha1:7d2b53f65bae3f16cf318103e53eb8350af6bd8a 2012-10-11T20:14:01Z Peter Stephenson pws@users.sourceforge.net 2012-10-11T20:14:01Z urn:sha1:4b86cc48f704152ccca13c50bc3acd59b4217ecc 2012-10-07T19:46:46Z Peter Stephenson pws@users.sourceforge.net 2012-10-07T19:46:46Z urn:sha1:4e2cdd795677e655f89b76b57611a196ce578432 from the emulate command 2009-02-11T20:42:15Z Peter Stephenson pws@users.sourceforge.net 2009-02-11T20:42:15Z urn:sha1:c7d8b0dfb8ae9670e2bc11ecf563200069a3a12f environments, plus documentation 2009-02-10T20:29:49Z Peter Stephenson pws@users.sourceforge.net 2009-02-10T20:29:49Z urn:sha1:51a646917a09f93f88ded76244780a09fae5acb0