项目中需要将LaTex公式转为图片传给前端,实现方式是利用exec分别调用系统的latex/dvips/convert命令,最终生成png文件.
...
error_reporting(0); # not checking existence myself, that would be double.
if (chdir("tmp")===FALSE) { return '[directory access error, fix permissions]'; } #I should chech whether file creation is allowed to give a nice error for that problem case
error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE); # TODO: set old value
$tfn = tempnam(getcwd(), 'PTX'); #file in tmp dir
#write temporary .tex file
if ( ($tex = fopen($tfn.'.tex', "w"))==FALSE) {
return '[file access error] '.phplatex_cleantmp($tfn,$heredir);
}
fwrite($tex, $totex);
fclose($tex);
# Run latex to create a .dvi. Have it try to fix minor errors instead of breaking/pausing on them.
exec($path_to_latex.' --interaction=nonstopmode '.$tfn.'.tex');
if (!file_exists($tfn.".dvi")) {
$log = file_get_contents($tfn.'.log'); #The log always exists, but now it's actually interesting since it'll contain an error
return '[latex error, code follows]<pre>'.$totex.'</pre><p><b>Log file:</b><pre>'.$log.'</pre></p> '.phplatex_cleantmp($tfn,$heredir);
}
...
某次出问题,报错一直都是’[latex error, code follows…]’,即执行完latex命令转换tex的代码后检查dvi文件是否存在,打印出exec执行的代码,’/usr/bin/latex –interaction=nonstopmode /tmp/PTXBmQJee.tex’,上文有 chdir(“tmp”) 已经切换到当前目录下的tmp目录,而此tex却在/tmp下,打印发现getcwd()确实是当前目录的tmp,WTF,搜了下tempnam:
tempnam
Description string tempnam ( string $dir , string $prefix )
Creates a file with a unique filename, with access permission set to 0600, in the specified directory. If the directory does not exist or is not writable, tempnam() may generate a file in the system’s temporary directory, and return the full path to that file, including its name.
dir不存在或者不可写的时候会取系统的临时目录,而前面的chdir的判断并没有确保tmp可写.给tmp加写权限即解决问题.
