Re: Noob libssh question

[Alan Dunn <amdunn@xxxxxxxxx>]

Maybe I'm missing something, but the only way I see ssh_channel_read
possibly returning SSH_AGAIN (-2) looking at the source in master is
in the last line of ssh_channel_read_timeout (in src/channels.c) if
len is large enough to cause an overflow.  Otherwise every other path
does not return SSH_AGAIN (assuming SSH_AGAIN != 0, -1, SSH_ERROR as
seems to be the case).  Actually, the documentation seems less
specific than it could be in that SSH_AGAIN shouldn't come back even
in non-blocking mode...

Though perhaps your binary is linking against a different version of
libssh than you expect?  This has certainly happened to me before with
both a system-installed package and the version I was hoping to use.

On Thu, Feb 6, 2014 at 8:10 PM, craig and heather <calhjh@xxxxxxxxx> wrote:
> I've made an Objective-C class called RemoteAccess to encapsulate all ssh
> functionality. I've attached it to this note.
>
>
> On Thu, Feb 6, 2014 at 3:49 PM, craig and heather <calhjh@xxxxxxxxx> wrote:
>>
>> Hello,
>>
>> I am using libssl to execute simple C programs between raspberry pi's.
>> These programs are simple SDL graphics applications similar to that listed
>> below that don't write anything to stderr (unless there is an error) or
>> stdout.
>>
>> I am also doing some remote file creation and deletion using the same
>> libssl functionality.
>>
>> When I remotely execute commands such as "touch runfile" or "rm runfile" I
>> can see 0 bytes are returned from ssh_channel_read function as would be
>> expected. However whenever I run one of my little C programs
>> ssh_channel_read always returns -2 but the program runs successfully on the
>> remote system.
>>
>> Is there something I need to do in my C programs to satisfy
>> ssh_channel_read?
>>
>> Thanks for looking
>>
>>
>> /*
>>  * A Smart Screen Module
>>  *
>>  * Sets the entire screen to a specified RGB color
>>  * Typical Call:
>>  *      colorscreen 0 255 0
>>  *
>>  * Concept and Implementation by: Craig A. Lindley
>>  * Last Update: 01/30/2014
>>  */
>>
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <unistd.h>
>> #include <sys/stat.h>
>> #include <sys/types.h>
>>
>> #include "SDL/SDL.h"
>>
>> #define RUN_FILE_NAME "runfile"
>> #define BUSY_FILE_NAME "busy"
>>
>> // Check for file existance
>> int file_exists(char *filename) {
>>
>>     struct stat buffer;
>>     return (stat (filename, &buffer) == 0);
>> }
>>
>> int main (int argc, char* args[]) {
>>
>>     if (argc != 4) {
>>         fprintf(stderr, "Wrong number of arguments\n");
>>         return -1;
>>     }
>>
>>     // Extract RGB values from the command line arguments
>>     int red   = atoi(args[1]);
>>     int green = atoi(args[2]);
>>     int blue  = atoi(args[3]);
>>
>>     // Range check the specified color values
>>     if ((red   < 0) || (red   > 255) ||
>>         (green < 0) || (green > 255) ||
>>         (blue  < 0) || (blue  > 255)) {
>>         fprintf(stderr, "Color values in range 0 <= value < 256\n");
>>         return -1;
>>     }
>>
>>     // Create the busy file
>>     FILE *pFile = fopen (BUSY_FILE_NAME,"w");
>>     if (pFile != NULL) {
>>         fclose(pFile);
>>     }    else    {
>>         fprintf(stderr, "Could not create busy file\n");
>>         return -1;
>>     }
>>
>>     putenv("SDL_FBDEV=/dev/fb1");
>>     putenv("SDL_VIDEODRIVER=fbcon");
>>
>>     // Start SDL
>>     SDL_Init(SDL_INIT_VIDEO);
>>
>>     // Turn off cursor
>>     SDL_ShowCursor(SDL_DISABLE);
>>
>>     const SDL_VideoInfo *videoInfo = SDL_GetVideoInfo();
>>
>>     int width  = videoInfo->current_w;
>>     int height = videoInfo->current_h;
>>     uint8_t bpp = videoInfo->vfmt->BitsPerPixel;
>>
>>     // Set up screen
>>     SDL_Surface *screen = SDL_SetVideoMode(width, height, bpp,
>> SDL_SWSURFACE);
>>     if (!screen) {
>>         fprintf(stderr, "SDL_SetVideoMode failed\n");
>>         return -1;
>>     }
>>     // Create the specified color
>>     uint32_t color = SDL_MapRGB(screen->format, red, green, blue);
>>
>>     // Create rect the size of the screen
>>     SDL_Rect rect = {0, 0, width, height};
>>
>>     // Fill the screen with the specified color
>>     SDL_FillRect(screen, &rect, color);
>>
>>     // Update Screen
>>     SDL_Flip(screen);
>>
>>     // Pause
>>     SDL_Delay(1000);
>>
>>     // Wait until runfile is gone to terminate
>>     while (file_exists(RUN_FILE_NAME)) {
>>         SDL_Delay(50);
>>     }
>>
>>     // Delete the busy file
>>     if (remove(BUSY_FILE_NAME) != 0) {
>>         fprintf(stderr, "Error deleting busy file\n");
>>     }
>>
>>     // Quit SDL
>>     SDL_Quit();
>>
>>     return 0;
>> }
>>
>>
>> --
>> Craig Lindley
>>
>> If you're one in a million, there are now seven thousand people exactly
>> like you.
>
>
>
>
> --
> Craig Lindley / Heather Hubbard
>
> New Recordings: craigandheather.net/cnmpage.html
> Latest CD: craigandheather.net/songsilike2013cd.html
>
> Personal Website: craigandheather.net
> Business Website: clockwork.craigandheather.net
> Phone: (719) 495-1873
> Cell: (719) 502-7925
>
> If you're one in a million, there are now seven thousand people exactly like
> you.