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Top Forums Shell Programming and Scripting Questions about file descriptors Post 302917476 by solaris_user on Wednesday 17th of September 2014 02:59:27 AM
Old 09-17-2014
Questions about file descriptors

Hi, I'm playing with KSH

I entered following command in terminal

Code:
{ echo "stdout" >&1; echo "stderr" >&2; } > out

And I get only stoud in a new file out.

My question is: Where did my stderr vanish ?
 

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POPEN(3)								 1								  POPEN(3)

popen - Opens process file pointer

SYNOPSIS
resource popen (string $command, string $mode) DESCRIPTION
Opens a pipe to a process executed by forking the command given by $command. PARAMETERS
o $command - The command o $mode - The mode RETURN VALUES
Returns a file pointer identical to that returned by fopen(3), except that it is unidirectional (may only be used for reading or writing) and must be closed with pclose(3). This pointer may be used with fgets(3), fgetss(3), and fwrite(3). When the mode is 'r', the returned file pointer equals to the STDOUT of the command, when the mode is 'w', the returned file pointer equals to the STDIN of the command. If an error occurs, returns FALSE. EXAMPLES
Example #1 popen(3) example <?php $handle = popen("/bin/ls", "r"); ?> If the command to be executed could not be found, a valid resource is returned. This may seem odd, but makes sense; it allows you to access any error message returned by the shell: Example #2 popen(3) example <?php error_reporting(E_ALL); /* Add redirection so we can get stderr. */ $handle = popen('/path/to/executable 2>&1', 'r'); echo "'$handle'; " . gettype($handle) . " "; $read = fread($handle, 2096); echo $read; pclose($handle); ?> NOTES
Note If you're looking for bi-directional support (two-way), use proc_open(3). Note When safe mode is enabled, you can only execute files within the safe_mode_exec_dir. For practical reasons, it is currently not allowed to have .. components in the path to the executable. Warning With safe mode enabled, the command string is escaped with escapeshellcmd(3). Thus, echo y | echo x becomes echo y | echo x. SEE ALSO
pclose(3), fopen(3), proc_open(3). PHP Documentation Group POPEN(3)
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