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More emphasis on os.environ's calling of putenv; and added hint about 

flags for open().
This commit is contained in:
Guido van Rossum 1997-08-08 21:05:09 +00:00
parent 7d6b7d3f54
commit 9c43c590bc
2 changed files with 28 additions and 8 deletions
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18
Doc/lib/libposix.tex
View File

@ -13,7 +13,9 @@ the \code{posix} interface. On non-\UNIX{} operating systems the
\code{posix} module is not available, but a subset is always available
through the \code{os} interface. Once \code{os} is imported, there is
\emph{no} performance penalty in using it instead of
\code{posix}.
\code{posix}. In addition, \code{os} provides some additional
functionality, such as automatically calling \code{putenv()}
when an entry is \code{os.environ} is changed.
\stmodindex{os}
The descriptions below are very terse; refer to the
@ -35,13 +37,17 @@ For example,
is the pathname of your home directory, equivalent to
\code{getenv("HOME")}
in C.
Modifying this dictionary does not affect the string environment
passed on by \code{execv()}, \code{popen()} or \code{system()}; if you
need to change the environment, pass \code{environ} to \code{execve()}
or add variable assignments and export statements to the command
string for \code{system()} or \code{popen()}.%
\footnote{The problem with automatically passing on \code{environ} is
that there is no portable way of changing the environment.}
string for \code{system()} or \code{popen()}.
\emph{However:} If you are using this module via the \code{os} module
(as you should -- see the introduction above), \code{environ} is a
a mapping object that behaves almost like a dictionary but invokes
\code{putenv()} automatically called whenever an item is changed.
\end{datadesc}
\renewcommand{\indexsubitem}{(exception in module posix)}
@ -238,6 +244,10 @@ The default \var{mode} is 0777 (octal), and the current umask value is
first masked out. Return the file descriptor for the newly opened
file.
For a description of the flag and mode values, see the \UNIX{} or C
run-time documentation; flag constants (like \code{O_RDONLY} and
\code{O_WRONLY}) are defined in this module too (see below).
Note: this function is intended for low-level I/O. For normal usage,
use the built-in function \code{open}, which returns a ``file object''
with \code{read()} and \code{write()} methods (and many more).

18
Doc/libposix.tex
View File

@ -13,7 +13,9 @@ the \code{posix} interface. On non-\UNIX{} operating systems the
\code{posix} module is not available, but a subset is always available
through the \code{os} interface. Once \code{os} is imported, there is
\emph{no} performance penalty in using it instead of
\code{posix}.
\code{posix}. In addition, \code{os} provides some additional
functionality, such as automatically calling \code{putenv()}
when an entry is \code{os.environ} is changed.
\stmodindex{os}
The descriptions below are very terse; refer to the
@ -35,13 +37,17 @@ For example,
is the pathname of your home directory, equivalent to
\code{getenv("HOME")}
in C.
Modifying this dictionary does not affect the string environment
passed on by \code{execv()}, \code{popen()} or \code{system()}; if you
need to change the environment, pass \code{environ} to \code{execve()}
or add variable assignments and export statements to the command
string for \code{system()} or \code{popen()}.%
\footnote{The problem with automatically passing on \code{environ} is
that there is no portable way of changing the environment.}
string for \code{system()} or \code{popen()}.
\emph{However:} If you are using this module via the \code{os} module
(as you should -- see the introduction above), \code{environ} is a
a mapping object that behaves almost like a dictionary but invokes
\code{putenv()} automatically called whenever an item is changed.
\end{datadesc}
\renewcommand{\indexsubitem}{(exception in module posix)}
@ -238,6 +244,10 @@ The default \var{mode} is 0777 (octal), and the current umask value is
first masked out. Return the file descriptor for the newly opened
file.
For a description of the flag and mode values, see the \UNIX{} or C
run-time documentation; flag constants (like \code{O_RDONLY} and
\code{O_WRONLY}) are defined in this module too (see below).
Note: this function is intended for low-level I/O. For normal usage,
use the built-in function \code{open}, which returns a ``file object''
with \code{read()} and \code{write()} methods (and many more).