08-02-2008
/*
* here's how you can do it...
* using popen()
*
#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define READ 0
#define WRITE 1
pid_t
popen2(const char *command, int *infp, int *outfp)
{
int p_stdin[2], p_stdout[2];
pid_t pid;
if (pipe(p_stdin) != 0 || pipe(p_stdout) != 0)
return -1;
pid = fork();
if (pid < 0)
return pid;
else if (pid == 0)
{
close(p_stdin[WRITE]);
dup2(p_stdin[READ], READ);
close(p_stdout[READ]);
dup2(p_stdout[WRITE], WRITE);
execl("/bin/sh", "sh", "-c", command, NULL);
perror("execl");
exit(1);
}
if (infp == NULL)
close(p_stdin[WRITE]);
else
*infp = p_stdin[WRITE];
if (outfp == NULL)
close(p_stdout[READ]);
else
*outfp = p_stdout[READ];
return pid;
}
/*
* now in main... infp will be the stdin (in file descriptor)
* and outfp will be the stdout (out file descriptor)
* have fun
*/
int
main(int argc, char **argv)
{
int infp, outfp;
char buf[128];
if (popen2("your-program-B", &infp, &outfp) <= 0)
{
printf("Unable to exec your-program-B\n");
exit(1);
}
memset (buf, 0x0, sizeof(buf));
write(infp, "Z\n", 2);
write(infp, "D\n", 2);
write(infp, "A\n", 2);
write(infp, "C\n", 2);
close(infp);
read(outfp, buf, 128);
printf("buf = '%s'\n", buf);
return 0;
}
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LEARN ABOUT NETBSD
start_transaction
START
TRANSACTION(7) SQL Commands START TRANSACTION(7)
NAME
START TRANSACTION - start a transaction block
SYNOPSIS
START TRANSACTION [ transaction_mode [, ...] ]
where transaction_mode is one of:
ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
READ WRITE | READ ONLY
DESCRIPTION
This command begins a new transaction block. If the isolation level or read/write mode is specified, the new transaction has those charac-
teristics, as if SET TRANSACTION [set_transaction(7)] was executed. This is the same as the BEGIN [begin(7)] command.
PARAMETERS
Refer to SET TRANSACTION [set_transaction(7)] for information on the meaning of the parameters to this statement.
COMPATIBILITY
In the standard, it is not necessary to issue START TRANSACTION to start a transaction block: any SQL command implicitly begins a block.
PostgreSQL's behavior can be seen as implicitly issuing a COMMIT after each command that does not follow START TRANSACTION (or BEGIN), and
it is therefore often called ``autocommit''. Other relational database systems might offer an autocommit feature as a convenience.
The SQL standard requires commas between successive transaction_modes, but for historical reasons PostgreSQL allows the commas to be omit-
ted.
See also the compatibility section of SET TRANSACTION [set_transaction(7)].
SEE ALSO
BEGIN [begin(7)], COMMIT [commit(7)], ROLLBACK [rollback(7)], SAVEPOINT [savepoint(7)], SET TRANSACTION [set_transaction(7)]
SQL - Language Statements 2010-05-14 START TRANSACTION(7)