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(Special Shell Variables): Mention _,

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BIN_SH, DUALCASE.  Say that variables other than "status" are safe
if they contain a lower-case letter.
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Paul Eggert 2005-02-03 00:31:33 +00:00
parent fda63f71a7
commit 4f6ba2b9e4
1 changed files with 28 additions and 1 deletions
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@ -10405,10 +10405,31 @@ Some shell variables should not be used, since they can have a deep
influence on the behavior of the shell. In order to recover a sane
behavior from the shell, some variables should be unset, but
@command{unset} is not portable (@pxref{Limitations of Builtins}) and a
fallback value is needed. We list these values below.
fallback value is needed.
As a general rule, shell variable names containing a lower-case letter
are safe; you can define and use these variables without worrying about
their effect on the underlying system, and without worrying about
whether the shell will change them unexpectedly. (The exception is the
shell variable @code{status}, as described below.)
Here is a list of names that are known to cause trouble. This list is
not exhaustive, but you should be safe if you avoid the name
@code{status} and names containing only upper-case letters and
underscores.
@c Alphabetical order, case insensitive, `A' before `a'.
@table @code
@item _
Many shells reserve @samp{$_} for various purposes, e.g., the name of
the last command executed.
@item BIN_SH
@evindex BIN_SH
In Tru64, if @env{BIN_SH} is set to @code{xpg4}, subsidiary invocations of
the standard shell conform to Posix.
Autoconf-generated scripts export this variable when they start up.
@item CDPATH
@evindex CDPATH
When this variable is set it specifies a list of directories to search
@ -10431,6 +10452,12 @@ In practice the shells that have this problem also support
Autoconf-generated scripts automatically unset @code{CDPATH} if
possible, so you need not worry about this problem in those scripts.
@item DUALCASE
@evindex DUALCASE
In the MKS shell, case statements and file name generation are
case-insensitive unless @code{DUALCASE} is nonzero.
Autoconf-generated scripts export this variable when they start up.
@item IFS
@evindex IFS
Don't set the first character of @code{IFS} to backslash. Indeed,