/* Redirects the output of a given CMD, as specified by toType and toFile. If
* the environment variable noclobber is set, > and >& may not redirect to
* existing files and >> and >>& must redirect to existing files; the ! versions
* of these redirection operators are not subject to these limitations.
*
* @simple = CMD to be redirected
*
* Returns: 0 on success, -1 on error
*/
int redirect_output(CMD* simple)
{
assert(simple->toFile);
int fdout;
int output_type = simple->toType;
int mode = O_WRONLY;
if (getenv("noclobber") && !(ISCLOBBER(output_type))) {
if (ISAPPEND(output_type)) {
mode |= O_APPEND;
} else {
mode |= O_CREAT | O_EXCL;
}
} else {
mode |= O_CREAT;
if (ISAPPEND(output_type)) {
mode |= O_APPEND;
} else {
mode |= O_TRUNC;
}
}
if ((fdout = open(simple->toFile, mode, 0755)) < 0) {
perror(simple->toFile);
return -1;
}
dup2(fdout, 1);
if (ISREDERR(simple->toType)) dup2(fdout, 2);
close(fdout);
return 0;
}
// Redirects using dup2() based on the given command's redirection
// fields. Returns 0 for success, -1 for failure. errno is set if -1 is returned
int redirect(CMD* cmd)
{
if(!cmd) return 0;
fflush(stdout);
fflush(stderr);
int fd;
if(cmd->fromType == RED_IN)
{
if((fd = open(cmd->fromFile, O_RDONLY)) < 0)
{
perror(EXEC_NAME);
return -1;
}
if(fd != STDIN_FD)
{
dup2(fd, STDIN_FD);
close(fd);
}
}
else if(cmd->fromType == RED_HERE)
{
// use a pipe for HERE documents; a child process will write the doc
// to a pipe, which the parent process will read
int fd[2];
int pid;
if(pipe(fd) || (pid = fork()) < 0)
{
perror(EXEC_NAME);
return -1;
}
else if(pid == 0)
{
// child
close(fd[0]);
if(fd[1] != STDOUT_FD)
{
dup2(fd[1], STDOUT_FD);
close(fd[1]);
}
for(char* c = cmd->fromFile; *c != '\0'; c++)
{
putchar(*c);
}
exit(EXIT_SUCCESS);
}
else
{
// parent
close(fd[1]);
if(fd[0] != STDIN_FD)
{
dup2(fd[0], STDIN_FD);
close(fd[0]);
}
}
}
if(cmd->toType != NONE)
{
int options = O_WRONLY;
if(ISAPPEND(cmd->toType))
{
options |= O_APPEND;
if(!getenv("noclobber") || ISCLOBBER(cmd->toType))
{
options |= O_CREAT;
}
}
else
{
options |= O_CREAT | O_TRUNC;
if(getenv("noclobber") && !ISCLOBBER(cmd->toType))
{
options |= O_EXCL;
}
}
if((fd = open(cmd->toFile, options, (mode_t)0666)) < 0)
{
perror(EXEC_NAME);
return -1;
}
dup2(fd, STDOUT_FD);
if(ISERROR(cmd->toType))
{
dup2(fd, STDERR_FD);
}
close(fd);
}
return 0;
}