jdb@mordor.UUCP (12/07/83)
I would recommend NOT changing system(), popen(), etc. to use SHELL.
It is desirable to have a standard interface that programs can rely
upon when performing a system() or popen(); this is not the case if
the shell which is used varies from one user to another. An example
is the "make" program -- a number of makefiles depend upon the use
of "/bin/sh" (which I believe is perfectly reasonable for them to do).
[An even better approach would be to specify the desired shell as an
equivalenced parameter in the makefile.]
Editors and other programs which have shell escapes should use SHELL
because the human who is typing input to them presumably wants to use
the same shell as his login shell. Non-interactive uses, however,
normally will "want" a predetermined shell.
I admit that system(), popen(), and friends are too useful to ignore
the possibility of other shells completely. Perhaps a new routine
("systemsh()"?) could be defined which would specify the command
interpreter that these routines would use, with "/bin/sh" still the
default. This way, programs that want "csh" can get it. It would
be necessary to explicitly define the shell to be used. Programs
could specify 'systemsh(getenv("SHELL"))'; hopefully, the fact that
an explicit specification is needed will cause the programmer to
think about whether the program will break if the user's login shell
is not the same as the programmer's.
--
John Bruner (S-1 Project, Lawrence Livermore National Laboratory)
MILNET: jdb@s1-c UUCP: ...!decvax!decwrl!mordor!jdb