+.BI filename_format \fR=\fPstr
+If sharing multiple files between jobs, it is usually necessary to have
+fio generate the exact names that you want. By default, fio will name a file
+based on the default file format specification of
+\fBjobname.jobnumber.filenumber\fP. With this option, that can be
+customized. Fio will recognize and replace the following keywords in this
+string:
+.RS
+.RS
+.TP
+.B $jobname
+The name of the worker thread or process.
+.TP
+.B $jobnum
+The incremental number of the worker thread or process.
+.TP
+.B $filenum
+The incremental number of the file for that worker thread or process.
+.RE
+.P
+To have dependent jobs share a set of files, this option can be set to
+have fio generate filenames that are shared between the two. For instance,
+if \fBtestfiles.$filenum\fR is specified, file number 4 for any job will
+be named \fBtestfiles.4\fR. The default of \fB$jobname.$jobnum.$filenum\fR
+will be used if no other format specifier is given.
+.RE
+.P
+.TP