## Tcl8.6.15/Tk8.6.15 Documentation > Tcl C API, version 8.6.15 > GetOpnFl

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### NAME

Tcl_GetOpenFile — Return a FILE* for a channel registered in the given interpreter (Unix only)

### SYNOPSIS

#include <tcl.h>
int
Tcl_GetOpenFile(interp, chanID, write, checkUsage, filePtr)

### ARGUMENTS

Tcl_Interp *interp (in)
  Tcl interpreter from which file handle is to be obtained.

const char *chanID (in)
  String identifying channel, such as stdin or file4.

int write (in)
  Non-zero means the file will be used for writing, zero means it will be used for reading.

int checkUsage (in)
  If non-zero, then an error will be generated if the file was not opened for the access indicated by write.

ClientData *filePtr (out)
  Points to word in which to store pointer to FILE structure for the file given by chanID.

### DESCRIPTION

Tcl_GetOpenFile takes as argument a file identifier of the form returned by the open command and returns at *filePtr a pointer to the FILE structure for the file. The write argument indicates whether the FILE pointer will be used for reading or writing. In some cases, such as a channel that connects to a pipeline of subprocesses, different FILE pointers will be returned for reading and writing. Tcl_GetOpenFile normally returns TCL_OK. If an error occurs in Tcl_GetOpenFile (e.g. chanID did not make any sense or checkUsage was set and the file was not opened for the access specified by write) then TCL_ERROR is returned and the interpreter's result will contain an error message. In the current implementation checkUsage is ignored and consistency checks are always performed.

Note that this interface is only supported on the Unix platform.

### KEYWORDS

channel, file handle, permissions, pipeline, read, write
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