zopen.3

早期freebsd实现

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.\"	@(#)zopen.3	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt ZOPEN 3
.Os
.Sh NAME
.Nm zopen
.Nd compressed stream open function
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Ft FILE *
.Fn zopen "const char *path" "const char *mode" "int bits"
.Sh DESCRIPTION
The
.Fn zopen
function
opens the compressed file whose name is the string pointed to by
.Fa path
and associates a stream with it.
.Pp
The argument
.Fa mode
points to one of the following one-character strings:
.Bl -tag -width indent
.It Dq Li r
Open compressed file for reading.
The stream is positioned at the beginning of the file.
.It Dq Li w
Truncate file to zero length or create compressed file for writing.
The stream is positioned at the beginning of the file.
.El
.Pp
Any created files will have mode
.Pf \\*q Dv S_IRUSR
\&|
.Dv S_IWUSR
\&|
.Dv S_IRGRP
\&|
.Dv S_IWGRP
\&|
.Dv S_IROTH
\&|
.Dv S_IWOTH Ns \\*q
.Pq Li 0666 ,
as modified by the process'
umask value (see
.Xr umask 2 ) .
.Pp
Files may only be read or written.
Seek operations are not allowed.
.Pp
The
.Fa bits
argument, if non-zero, is set to the bits code limit.
If zero, the default is 16.
See
.Fn compress 1
for more information.
.Sh RETURN VALUES
Upon successful completion
.Fn zopen
returns a
.Tn FILE
pointer.
Otherwise,
.Dv NULL
is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Bl -tag -width [EINVAL]
.It Bq Er EINVAL
The
.Fa mode
or
.Fa bits
arguments specified to
.Fn zopen
were invalid.
.It Bq Er EFTYPE
The compressed file starts with an invalid header, or the compressed
file is compressed with more bits than can be handled.
.El
.Pp
The
.Fn zopen
function may also fail and set
.Va errno
for any of the errors specified for the routines
.Xr fopen 3
or
.Xr funopen 3 .
.Sh SEE ALSO
.Xr compress 1 ,
.Xr fopen 3 ,
.Xr funopen 3
.Sh HISTORY
The
.Nm zopen
function
first appeared in 4.4BSD.
.Sh BUGS
The
.Fn zopen
function
may not be portable to systems other than
.Bx .