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File name : emulate

Content :emulate [ -lLR ] [ {zsh|sh|ksh|csh} [ flags ... ] ] Without any argument print current emulation mode. With single argument set up zsh options to emulate the specified shell as much as possible. csh will never be fully emulated. If the argument is not one of the shells listed above, zsh will be used as a default; more precisely, the tests performed on the argument are the same as those used to determine the emulation at startup based on the shell name, see the section COMPATIBIL- ITY in zsh(1) . In addition to setting shell options, the com- mand also restores the pristine state of pattern enables, as if all patterns had been enabled using enable -p. If the emulate command occurs inside a function that has been marked for execution tracing with functions -t then the xtrace option will be turned on regardless of emulation mode or other options. Note that code executed inside the function by the ., source, or eval commands is not considered to be running di- rectly from the function, hence does not provoke this behaviour. If the -R switch is given, all settable options are reset to their default value corresponding to the specified emulation mode, except for certain options describing the interactive en- vironment; otherwise, only those options likely to cause porta- bility problems in scripts and functions are altered. If the -L switch is given, the options LOCAL_OPTIONS, LOCAL_PATTERNS and LOCAL_TRAPS will be set as well, causing the effects of the emu- late command and any setopt, disable -p or enable -p, and trap commands to be local to the immediately surrounding shell func- tion, if any; normally these options are turned off in all emu- lation modes except ksh. The -L switch is mutually exclusive with the use of -c in flags. If there is a single argument and the -l switch is given, the options that would be set or unset (the latter indicated with the prefix `no') are listed. -l can be combined with -L or -R and the list will be modified in the appropriate way. Note the list does not depend on the current setting of options, i.e. it includes all options that may in principle change, not just those that would actually change. The flags may be any of the invocation-time flags described in the section INVOCATION in zsh(1), except that `-o EMACS' and `-o VI' may not be used. Flags such as `+r'/`+o RESTRICTED' may be prohibited in some circumstances. If -c arg appears in flags, arg is evaluated while the requested emulation is temporarily in effect. In this case the emulation mode and all options are restored to their previous values be- fore emulate returns. The -R switch may precede the name of the shell to emulate; note this has a meaning distinct from includ- ing -R in flags. Use of -c enables `sticky' emulation mode for functions defined within the evaluated expression: the emulation mode is associ- ated thereafter with the function so that whenever the function is executed the emulation (respecting the -R switch, if present) and all options are set (and pattern disables cleared) before entry to the function, and the state is restored after exit. If the function is called when the sticky emulation is already in effect, either within an `emulate shell -c' expression or within another function with the same sticky emulation, entry and exit from the function do not cause options to be altered (except due to standard processing such as the LOCAL_OPTIONS option). This also applies to functions marked for autoload within the sticky emulation; the appropriate set of options will be applied at the point the function is loaded as well as when it is run. For example: emulate sh -c 'fni() { setopt cshnullglob; } fno() { fni; }' fno The two functions fni and fno are defined with sticky sh emula- tion. fno is then executed, causing options associated with em- ulations to be set to their values in sh. fno then calls fni; because fni is also marked for sticky sh emulation, no option changes take place on entry to or exit from it. Hence the op- tion cshnullglob, turned off by sh emulation, will be turned on within fni and remain on return to fno. On exit from fno, the emulation mode and all options will be restored to the state they were in before entry to the temporary emulation. The documentation above is typically sufficient for the intended purpose of executing code designed for other shells in a suit- able environment. More detailed rules follow. 1. The sticky emulation environment provided by `emulate shell -c' is identical to that provided by entry to a function marked for sticky emulation as a consequence of being defined in such an environment. Hence, for exam- ple, the sticky emulation is inherited by subfunctions defined within functions with sticky emulation. 2. No change of options takes place on entry to or exit from functions that are not marked for sticky emulation, other than those that would normally take place, even if those functions are called within sticky emulation. 3. No special handling is provided for functions marked for autoload nor for functions present in wordcode created by the zcompile command. 4. The presence or absence of the -R switch to emulate cor- responds to different sticky emulation modes, so for ex- ample `emulate sh -c', `emulate -R sh -c' and `emulate csh -c' are treated as three distinct sticky emulations. 5. Difference in shell options supplied in addition to the basic emulation also mean the sticky emulations are dif- ferent, so for example `emulate zsh -c' and `emulate zsh -o cbases -c' are treated as distinct sticky emulations.

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