Here are more specific details: I use GNU/Linux Ubuntu 8.04 on an
x86_64 workstation. R environnement was compiled from 2.8.0 sources.
Below is a part of my C code to test the file I/O.
When compiled as a standalone executable it prints "Test 1" on the
console and generates "test.txt" and "test.png" file outputs as
expected. When compiled as a shared library and invoked from R
environment via .C() interface, it does nothing (to avoid any file
access issue, file permissions were set to 777 in the "/test" output
folder).
Am I missing a configuration option?
Thanks for your help,
----
#include <R.h>
#include <Rmath.h>
#include <stdio.h>
#include <gd.h>
//
------------------------------------------------------------------------------
void c_bricks(double *x, int *nx, int *nw, double *gamma, double
*Piw, double *V, double *W) {
fflush(stdout);
printf("Test %10d\n", 1);
Rprintf("Test %10d\n", 2);
REprintf("Test %10d\n", 3);
FILE *txtlog;
txtlog = fopen("/test/test.txt", "w");
fprintf(txtlog, "Test %10d\n", 1);
fclose(txtlog);
// *** Code imported from the GD2 tutorial,
http://www.libgd.org/Manual ***
// Declare the image
gdImagePtr im;
// Declare output files
FILE *pngout;
// Declare color indexes
int black;
int white;
// Allocate the image: 64 pixels across by 64 pixels tall
im = gdImageCreate(64, 64);
/* Allocate the color black (red, green and blue all minimum).
Since this is the first color in a new image, it will
be the background color. */
black = gdImageColorAllocate(im, 0, 0, 0);
/* Allocate the color white (red, green and blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);
/* Draw a line from the upper left to the lower right,
using white color index. */
gdImageLine(im, 0, 0, 63, 63, white);
/* Open a file for writing. "wb" means "write binary", important
under MSDOS, harmless under Unix. */
pngout = fopen("/test/test.png", "wb");
/* Output the image to the disk file in PNG format. */
gdImagePng(im, pngout);
/* Close the files. */
fclose(pngout);
/* Destroy the image in memory. */
gdImageDestroy(im);
}
Prof Brian Ripley a écrit :
On Wed, 28 Jan 2009, Benjamin Leblanc wrote:
Hello all,
I am getting into trouble when trying to do standard I/O from a C
function called within R environment.
This function is written in a small C library that is loaded whith
dyn.load() and called in R via the .C() interface. I need to debug
the C code using a text file for some logs, and also to speed up
its result visualization by creating images on the fly using the GD
library.
Both of these outputs require to write into files from this C
function.
Allthough everything goes smoothly from compilation and linking to
execution into R without errors, no file is created. I have also
tried to do some simple printf(), Rprintf() and REprintf() but even
that didn't gave me any visible output.
Am I missing something trivial? Could anyone give me a hint on why
it does not work?
It works in many other packages. What OS are you using? (There
known issues with using stdout and stderr from GUIs, but those are
documented in the R-exts manual.)
Best regards,
Benjamin
--
Chromatin and Cell Biology Lab.
Institute for Human Genetics
141, rue de la Cardonille
F-34396 Montpellier
France
Phone +33-(0)4 99 61 99 51
FAX +33-(0)4 99 61 99 01
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