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.\" ========================================================================
.\"
.IX Title "SDBM_File 3"
.TH SDBM_File 3 "2002-11-24" "perl v5.8.0" "Perl Programmers Reference Guide"
.SH "NAME"
SDBM_File \- Tied access to sdbm files
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& use Fcntl;   # For O_RDWR, O_CREAT, etc.
\& use SDBM_File;
.Ve
.PP
.Vb 2
\& tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
\&   or die "Couldn't tie SDBM file 'filename': $!; aborting";
.Ve
.PP
.Vb 4
\& # Now read and change the hash
\& $h{newkey} = newvalue;
\& print $h{oldkey}; 
\& ...
.Ve
.PP
.Vb 1
\& untie %h;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`SDBM_File\*(C'\fR establishes a connection between a Perl hash variable and
a file in SDBM_File format;.  You can manipulate the data in the file
just as if it were in a Perl hash, but when your program exits, the
data will remain in the file, to be used the next time your program
runs.
.PP
Use \f(CW\*(C`SDBM_File\*(C'\fR with the Perl built-in \f(CW\*(C`tie\*(C'\fR function to establish
the connection between the variable and the file.  The arguments to
\&\f(CW\*(C`tie\*(C'\fR should be:
.IP "1." 4
The hash variable you want to tie.
.IP "2." 4
The string \f(CW"SDBM_File"\fR.  (Ths tells Perl to use the \f(CW\*(C`SDBM_File\*(C'\fR
package to perform the functions of the hash.)
.IP "3." 4
The name of the file you want to tie to the hash.  
.IP "4." 4
Flags.  Use one of:
.RS 4
.ie n .IP """O_RDONLY""" 2
.el .IP "\f(CWO_RDONLY\fR" 2
.IX Item "O_RDONLY"
Read-only access to the data in the file.
.ie n .IP """O_WRONLY""" 2
.el .IP "\f(CWO_WRONLY\fR" 2
.IX Item "O_WRONLY"
Write-only access to the data in the file.
.ie n .IP """O_RDWR""" 2
.el .IP "\f(CWO_RDWR\fR" 2
.IX Item "O_RDWR"
Both read and write access.
.RE
.RS 4
.Sp
If you want to create the file if it does not exist, add \f(CW\*(C`O_CREAT\*(C'\fR to
any of these, as in the example.  If you omit \f(CW\*(C`O_CREAT\*(C'\fR and the file
does not already exist, the \f(CW\*(C`tie\*(C'\fR call will fail.
.RE
.IP "5." 4
The default permissions to use if a new file is created.  The actual
permissions will be modified by the user's umask, so you should
probably use 0666 here. (See \*(L"umask\*(R" in perlfunc.)
.SH "DIAGNOSTICS"
.IX Header "DIAGNOSTICS"
On failure, the \f(CW\*(C`tie\*(C'\fR call returns an undefined value and probably
sets \f(CW$!\fR to contain the reason the file could not be tied.
.ie n .Sh """sdbm store returned \-1, errno 22, key ""..."" at ..."""
.el .Sh "\f(CWsdbm store returned \-1, errno 22, key ``...'' at ...\fP"
.IX Subsection "sdbm store returned -1, errno 22, key ""..."" at ..."
This warning is emmitted when you try to store a key or a value that
is too long.  It means that the change was not recorded in the
database.  See \s-1BUGS\s0 \s-1AND\s0 \s-1WARNINGS\s0 below.
.SH "BUGS AND WARNINGS"
.IX Header "BUGS AND WARNINGS"
There are a number of limits on the size of the data that you can
store in the \s-1SDBM\s0 file.  The most important is that the length of a
key, plus the length of its associated value, may not exceed 1008
bytes.
.PP
See \*(L"tie\*(R" in perlfunc, perldbmfilter, Fcntl