PHP: Flujos de E/S

[edit] Last updated: Fri, 07 Jun 2013

Flujos de entrada/salida

CLI SAPI define algunas constantes para flujos de E/S que simplifican la programación en línea de comandos.

**Constantes específicas de CLI**
Constante	Descripción
`STDIN`	Flujo abierto a stdin. Ahorra tener que abrirlo con `<?php $stdin = fopen('php://stdin', 'r'); ?>` Si se desea leer una sola línea de stdin, puede usarse `<?php $line = trim(fgets(STDIN)); // lee una línea de STDIN fscanf(STDIN, "%d\n", $number); // lee un número de STDIN ?>`
`STDOUT`	Flujo abierto a stdout. Ahorra tener que abrirlo con `<?php $stdout = fopen('php://stdout', 'w'); ?>`
`STDERR`	Flujo abierto a stderr. Ahora tener que abrirlo con `<?php $stderr = fopen('php://stderr', 'w'); ?>`

Teniendo esto en cuenta, no es necesario abrir por ejemplo un flujo a stderr, sino que puede usarse la constante en lugar del recurso de tipo flujo:

php -r 'fwrite(STDERR, "stderr\n");'

No es necesario cerrar explícitamente estos flujos, ya que se cierra automáticamente por PHP al finalizar el script.

Nota:
Estas constantes no están disponibles si se leyera el script PHP a partir de stdin.

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[edit] Last updated: Fri, 07 Jun 2013

add a note User Contributed Notes Flujos de E/S - [3 notes]

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ecrist at secure-computing dot net ¶

1 year ago


The following code shows how to test for input on STDIN.  In this case, we were looking for CSV data, so we use fgetcsv to read STDIN, if it creates an array, we assume CVS input on STDIN, if no array was created, we assume there's no input from STDIN, and look, later, to an argument with a CSV file name.



Note, without the stream_set_blocking() call, fgetcsv() hangs on STDIN, awaiting input from the user, which isn't useful as we're looking for a piped file. If it isn't here already, it isn't going to be.



<?php

stream_set_blocking(STDIN, 0);

$csv_ar = fgetcsv(STDIN);

if (is_array($csv_ar)){

  print "CVS on STDIN\n";

} else {

  print "Look to ARGV for CSV file name.\n";

}

?>

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Aurelien Marchand ¶

2 years ago


Please remember in multi-process applications (which are best suited under CLI), that I/O operations often will BLOCK signals from being processed.



For instance, if you have a parent waiting on fread(STDIN), it won't handle SIGCHLD, even if you defined a signal handler for it, until after the call to fread has returned. 



Your solution in this case is to wait on stream_select() to find out whether reading will block. Waiting on stream_select(), critically, does NOT BLOCK signals from being processed. 



Aurelien

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-2

James Zhu ¶

2 years ago


Example:





<?php


function ReadStdin($prompt, $valid_inputs, $default = '') {


    while(!isset($input) || (is_array($valid_inputs) && !in_array($input, $valid_inputs)) || ($valid_inputs == 'is_file' && !is_file($input))) {


        echo $prompt;


        $input = strtolower(trim(fgets(STDIN)));


        if(empty($input) && !empty($default)) {


            $input = $default;


        }


    }


    return $input;


}





// you can input <Enter> or 1, 2, 3


$choice = ReadStdin('Please choose your answer or press Enter to continue: ', array('', '1', '2', '3'));





// check input is valid file name, use /var/path for input nothing


$file = ReadStdin('Please input the file name(/var/path):', 'is_file', '/var/path');


?>





you can add more functions if you want.

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