Thread

1. C functions, arguments, and ssh oh my!

   Joel Dudley <joel.dudley@developonline.com> — 2001-03-27T19:25:32Z

   Hello All,
     I am writing my first C function for postgres and failing miserably. my C
   function needs to get passed a username (char) , uid(int), and gid(int) and
   what it does with those is builds a command string for an external app that
   is called with system() and exits 0. I know this is strange and ugly but I
   need to trigger this external app when an insert is made into a user table.
   I am looking into the version 1 calling convention to get these arguments
   into my C function but I can't seem to match the types correctly. I am
   looking at SPI with triggers now but I don't know if that will work either.
   Am I barking up the wrong tree here? any comments are appreciated and I
   appreciate the time you have taken to read my post.  Below is to cludgy poor
   code I have so far (it doesnt work of course) and I am halfway between
   converting to version 1 calling but I wanted to give you an idea of what I
   am trying to do. Thanks again.
   
   - Joel
   
   #include <stdlib.h>
   #include "postgres.h"
   #include "fmgr.h"
    
   /*int *ssh_exec(char *uname[FILENAME_MAX], char *uid[FILENAME_MAX], char
   *gid[FILENAME_MAX])*/
    
   PG_FUNCTION_INFO_V1(ssh_exec);
    
   Datum
   ssh_exec(PG_FUNCTION_ARGS)
   {
           char sshcmd[255];
    
           strncpy(sshcmd, "/usr/local/bin/plsshexec ", 255);
           strncat(sshcmd, *uname, 255);
           strncat(sshcmd, " ", 255);
           strncat(sshcmd, *uid, 255);
           strncat(sshcmd, " ", 255);
           strncat(sshcmd, *gid, 255);
           system(sshcmd);
           return 0;
   }
   
   

2. Re: C functions, arguments, and ssh oh my!

   Alfred Perlstein <bright@wintelcom.net> — 2001-03-27T19:31:28Z

   * Joel Dudley <Joel.Dudley@DevelopOnline.com> [010327 11:29] wrote:
   > Hello All,
   >   I am writing my first C function for postgres and failing miserably. my C
   > function needs to get passed a username (char) , uid(int), and gid(int) and
   
   right, wrong and wrong.
   
   char *, uid_t, gid_t.
   
   
   
   -- 
   -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
   Instead of asking why a piece of software is using "1970s technology,"
   start asking why software is ignoring 30 years of accumulated wisdom.
   
   

3. Re: C functions, arguments, and ssh oh my!

   Tom Lane <tgl@sss.pgh.pa.us> — 2001-03-27T19:51:40Z

   Joel Dudley <Joel.Dudley@DevelopOnline.com> writes:
   > what it does with those is builds a command string for an external app that
   > is called with system() and exits 0. I know this is strange and ugly but I
   > need to trigger this external app when an insert is made into a user table.
   
   This seems an extremely dubious practice.  If the transaction doing the
   insert is later rolled back, the insert effectively never happened ---
   but the effects of your external app will still be there.  I'd suggest
   thinking twice about your whole system design, if it requires this.
   
   You can mitigate the problem a little bit by making the trigger an
   AFTER trigger, so that it's only fired when we are about to commit the
   transaction.  But there's still a possibility of trouble if a later
   AFTER trigger decides to abort.
   
   			regards, tom lane
   
   

4. Re: C functions, arguments, and ssh oh my!

   Peter Eisentraut <peter_e@gmx.net> — 2001-03-27T19:55:48Z

   Joel Dudley writes:
   
   > PG_FUNCTION_INFO_V1(ssh_exec);
   >
   > Datum
   > ssh_exec(PG_FUNCTION_ARGS)
   > {
   >         char sshcmd[255];
   >
   >         strncpy(sshcmd, "/usr/local/bin/plsshexec ", 255);
   >         strncat(sshcmd, *uname, 255);
   >         strncat(sshcmd, " ", 255);
   >         strncat(sshcmd, *uid, 255);
   >         strncat(sshcmd, " ", 255);
   >         strncat(sshcmd, *gid, 255);
   >         system(sshcmd);
   >         return 0;
   > }
   
   You missed the part about fetching the arguments using PG_GETARG_xxx.
   Also you should use PG_RETURN_xxx and you need to null-terminate your
   string.
   
   -- 
   Peter Eisentraut      peter_e@gmx.net       http://yi.org/peter-e/