Thread: Calling SAC commands from C program

Hi,

On Thu, Oct 10 at 09:39, mohit agrawal wrote:

Hello SAC users,

I want to add a line something like this in a C program

*sprintf(str,"cd rdtmp; sac; r *.SAC; interpolate delta 1.0; w over; quit;
../%s");
system(str);*

This is really about C programming and command execution environment
rather than SAC. You might find more help on a general linux programming
list, but here goes.

The SAC commands need to be presented to the SAC program on it's standard
input, not as separate commands to be executed by the system shell. You
need to use popen() rather than system() so as to give you access to the
standard input pipline. Try this:

FILE *fp;

/* Start the SAC process with write access to stdin */
fp = popen( "cd rdtmp; sac", "we" );

/* Send the SAC commands to the process */
fprintf( fp, "%s", "r *.SAC\ninterpolate delta 1.0\nw over\nquit\n" );

/* Cloes the pipe and wait for SAC process to complete */
pclose( fp );

This example is untested, has no error checking and assumes that you want
the output from the SAC command to go to the current standard output, but
I hope you get the idea.

If you want to capture the output as well things get more complex. With
full error checking, handling stdin and stdout and all the potential locking
issues that implies it about 150 lines of code to do it right.

Any suggestion in this regard will be appreciated.

HTH

--
Bob Dunlop
Guralp Systems Limited
http://www.guralp.com