从窗体中检索值并写入文件 [英] Retrieve value from a form and write to a file

问题描述

我有一个名为

index.cgi

以及一个名为

$ b的配置文件
$ b

用户从下拉菜单中选择并按下提交后，该值将被读取并写入配置文件。以下是我的表单中的代码片段：

 < tr>< td> 
< form method =POSTaction =index.cgi> 
< table> 
< tr>< th colspan =2>视频< / th>< / tr> 
< tr>< td align =right>< b>视频来源：< / b>< / td>< td align =left> 
< select name =channel1size =1> 
 < option value =/ dev / video1> / dev / video1< / option> 
 < option value =/ dev / video3> / dev / video3< / option> 
< / select> 
< / td>< / tr> 
< / table> 
< / td>< / tr> 
< tr> 
< td colspan =2> 
< div id =button> 
< input type =submitvalue =Submit>< input type =resetvalue =Clear> 
< / div> 
< / form> 
< / td> 
< / tr> 
  

以下是来自 index.cgi ：

  my $ file =video.start; 
 
 open（my $ in，+<，$ file）; 
 open（my $ out，+<，$ file）; 
 
 my $ a = CGI-> new（）; 
 $ video = $ a-> param（'channel1'）; $（< $ in>）
 {
 print $ out $ _; 
 
 
最后如果$。== 3; 
 
 
 while（my $ data =< $ in>）
 {
 #logic 
 
 print $ out $ data; 
最后如果$。== 5; 
 
 $ / code> 

最后，这是我的配置文件的样子：

 ＃仅在[udp：//＃]段更改
＃此配置文件适用于视频
 
 ffmpeg -f video4linux2 -i / dev / video0 -vcodec libx264 -preset ultrafast -tune zerolatency -s qvga -r 30 -qscale 5 -an -flags low_delay -bsf：v h264_mp4toannexb -maxrate 750k -bufsize 3000k -rtbufsize 300k -f h264 udp：//＃
  

如果您从配置表单中可以看到用户提交值后，根据用户提交的值， / dev / video0 将在配置文件中更改。但是我怎么能在我的逻辑中实现这一点？

解决方案

最大的窍门是你需要 flock 编辑文件之前，比赛条件。



  use strict; 
使用警告; 
使用autodie; 
 
使用Fcntl qw（：flock）; 
 
打开我的$ fh，'< +'，'foobar.txt'; 
 flock（$ fh，LOCK_EX）或死无法锁定邮箱 -  $！\\\
; 
  

之后，请阅读 如何在文件中更改，删除或插入一行，或者追加到文件的开头？ 。我个人会选择 Tie :: File ，因为我认为这可能是编辑文件的最简单方法。

i have a form named

index.cgi

and a configuration file named

video.start

After the user select from the drop down menu and press submit, the value will be read and write into the configuration file. Here is a snippet from my form:

<tr><td>
<form method="POST" action="index.cgi">
<table>
<tr><th colspan="2">Video</th></tr>
<tr><td align="right"><b>Video Source :</b></td><td align="left">
<select name="channel1" size="1">
<option value="/dev/video0">/dev/video0</option>
<option value="/dev/video1">/dev/video1</option>
<option value="/dev/video2">/dev/video2</option>
<option value="/dev/video3">/dev/video3</option>
</select>
</td></tr>
</table>
</td></tr>
<tr>
<td colspan="2">
<div id="button">
<input type="submit" value="Submit"><input type="reset" value="Clear">
</div>
</form>
</td>
</tr>

and here is the code from index.cgi:

my $file = "video.start";

open (my $in, "+<", $file);
open (my $out, "+<", $file);

my $a = CGI->new();
$video = $a->param('channel1');

while(<$in>)
{
    print $out $_;
    last if $.==3;
}

while(my $data = <$in>)   
{
    #logic

    print $out $data;
    last if $.==5;
}

Finally, here is what my configuration file looks like:

#Only change at [udp://#] segment 
#This config file is for video

ffmpeg -f video4linux2 -i /dev/video0 -vcodec libx264 -preset ultrafast -tune zerolatency -s qvga -r 30 -qscale 5 -an -flags low_delay -bsf:v h264_mp4toannexb -maxrate 750k -bufsize 3000k -rtbufsize 300k -f h264 udp://# 

If you can see from the configuration form, after the user submitted the value, the /dev/video0 will change in the configuration file according to the value submitted by the user. But how can i achieve this in my logic?

解决方案

The biggest trick to this is that you need to flock your files before editing them so there isn't a race condition.

use strict;
use warnings;
use autodie;

use Fcntl qw(:flock);

open my $fh, '<+', 'foobar.txt';
flock($fh, LOCK_EX) or die "Cannot lock mailbox - $!\n";

After that, just read How do I change, delete, or insert a line in a file, or append to the beginning of a file?. I personally would go with Tie::File as I think that's probably the easiest way to edit a file in this context.

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