Alex Riesen <raa.lkml@xxxxxxxxx> writes:
> Others already discussed the issue. Just to be sure, I reimplemented
> that comfortable putenv with unsetenv: if an environment entry ends
> with a "=" it will be unset.
Although combination of putenv and unsetenv gives a somewhat
queasy feeling for obvious reasons, I'll let it pass. As we
are coming up with an interface that uses only one string per
environment element, that is probably a sensible thing to do,
rather than trying to do the "historically correct" pairing of
setenv/unsetenv.
However, I do not think "VAR=" to unset it is a good interface.
Having an environment variable whose value happens to be an
empty string and not having the variable at all are two
different things.
Because you _scan_ the whole string in your patch to see if it
ends with = anyway, a trivial improvement would be to do:
if (strchr(cmd->env, '='))
putenv(cmd->env);
else
unsetenv(cmd->env);
If you do not mind such a special syntax (e.g. "VAR="), I would
suggest doing that as a prefix (e.g. "!VAR") and do:
if (cmd->env[0] != '!')
putenv(cmd->env);
else
unsetenv(cmd->env + 1);
The former look cleaner but less efficient; we are going to exec
so I do not think micro-optimization would matter at all, so my
suggestion would be to do the strchr().
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