write(lnk,system ("sh","date"));

write(lnk,system ("sh","date > a"));

OR

write(lnk,system ("sh","date >> a"));

link lnk=":a file.txt"            // Note the :a part. The link should be appendable, not just writable.
open(lnk);
do_your_process;
close(lnk);
write(lnk,system ("sh","date >> a"));             // Note the >> redirection. If you put just one > then it will erase the whole
                                                  // file and just put the date.
open(lnk);
do_remaining_proces;
close(lnk);

system("sh","date")

write(lnk,system ("sh","date"));

string lnkname = "file.dat";   
write(">"+lnkname,"123");             // creates and write to file.date
write(">>"+lnkname,"hello");        // appends to the file
int errcode = system("sh","date >> " + lnkname);  // append the date to file.dat
write(">>"+lnkname,"the end");
read(lnkname);    // returns the whole file as a string

proc timestamp()
{
// returns the date as a string
int errcode;
string fnm =  "/tmp/date"+string(system("pid"))+".sig";  // create unique name
errcode = system("sh","date > "+fnm);
string date = read(fnm);
date[size(date)]="";                   // remove endining newline
errcode = system("sh","rm -f "+fnm);   // remove the date-file
return(date);
}

> timestamp();
Mi 25. Aug 15:21:10 CEST 2010

link lnk=":a file.txt";  // Note the :a part. The link is  appendabble not  just writable.
open(lnk);
// do_your_process;
write(lnk,timestamp());   // write the date to the file
// do_remaining_proces;
close(lnk);

system ("sh","compile_and_execute_batch_script");