You want to read the output from a program. For example, you want the output of a system utility, such as route(8), that provides network information.
To read the entire contents of a program’s output, use the backtick (`) operator:
|
1 |
$routing_table = `/sbin/route`; |
To read the output incrementally, open a pipe with popen():
|
1 2 3 4 5 |
$ph = popen('/sbin/route','r') or die($php_errormsg); while (! feof($ph)) { $s = fgets($ph) or die($php_errormsg); } pclose($ph) or die($php_errormsg); |
The backtick operator executes a program and returns all its output as a single string.
On a Linux system with 1.6 GB of RAM, the command $s = /usr/bin/free; puts the following multiline string in $s:
|
1 2 3 4 |
total used free shared buffers cached Mem: 16471704 15488260 983444 0 627820 12076120 -/+ buffers/cache: 2784320 13687384 Swap: 0 0 0 |
If a program generates a lot of output, it is more memory efficient to read from a pipe one line at a time.
If you’re printing formatted data to the browser based on the output of the pipe, you can print it as you get it.
This example prints information about recent Unix system logins formatted as an HTML table. It uses the /usr/bin/last command:
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 |
// print table header print<<<_HTML_ <table> <tr> <td>user</td><td>login port</td><td>login from</td><td>login time</td> <td>time spent logged in</td> </tr> _HTML_; // open the pipe to /usr/bin/last $ph = popen('/usr/bin/last','r') or die($php_errormsg); while (! feof($ph)) { $line = fgets($ph) or die($php_errormsg); // don't process blank lines or the info line at the end if (trim($line) && (! preg_match('/^wtmp begins/',$line))) { $user = trim(substr($line,0,8)); $port = trim(substr($line,9,12)); $host = trim(substr($line,22,16)); $date = trim(substr($line,38,25)); $elapsed = trim(substr($line,63,10),' ()'); if ('logged in' == $elapsed) { $elapsed = 'still logged in'; $date = substr_replace($date,'',-5); } print "<tr><td>$user</td><td>$port</td><td>$host</td>"; print "<td>$date</td><td>$elapsed</td></tr>\n"; } } pclose($ph) or die($php_errormsg); print '</table>'; |
