**CIGAL Reference Manual, Chapter 6 (RealTime): r_fopen**
===== r_fopen -- Open a file for reading or writing =====
**usage: r_fopen opflg eflag ltime Filename Lunit [Writeflag  Asyncflag]**

R_FOPEN is a REALTIME operator. It opens the named file and assigns it a
channel reference number; this reference number is returned in the LUNIT
argument.  If no LUNIT is specified then the file is assigned to channel 1
by default.

The file is opened for reading by default.  If WRITEFLAG is non-zero the
file can also be written to.  If ASYNCFLAG is specified and non-zero this
command starts the operation and returns without waiting for completion;
the default is to wait until the entire operation has completed.

Note 1: If no free channel is found or if there is an error in opening the file LUNIT is set to 0.

Note 2: Although this operator appears to function synchronously, it actually
involves asynchronous file operations; this allows other REALTIME
processing streams to continue while R_FOPEN awaits completion.

**See Also:**\\
[[jvs:cigal|CIGAL Home]], 
[[jvs:cigal:manual|CIGAL Manual]], 
[[jvs:cigal:manual:chapter6|RealTime List]], 
[[jvs:cigal:manual:help|Manual Help]]