不成功的使用的popen()在C? [英] unsuccesful use of popen() in C?
问题描述
我可以运行下面的命令
XWD -root | xwdtopnm | pnmtojpeg> screen.jpg
在linux下的一个终端,它会产生我当前屏幕的屏幕截图。
in a terminal under linux and it will produce a screenshot of my current screen.
我尝试做与code以下内容:
I try to do the following with the code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *fpipe;
char *command="xwd -root | xwdtopnm | pnmtojpeg";
char line[256];
if ( !(fpipe = (FILE*)popen(command,"r")) )
{ // If fpipe is NULL
perror("Problems with pipe");
exit(1);
}
while ( fgets( line, sizeof line, fpipe))
{
//printf("%s", line);
puts(line);
}
pclose(fpipe);
}
然后我编译并运行程序 ./的popen&GT; screen.jpg
但是产生的文件screen.jpg是unrecongizable。我怎样才能做到这一点,这样我就可以通过管我的程序是否正确?
then I compile and run the program ./popen > screen.jpg
but the resulting file screen.jpg is unrecongizable. How can I do this so that I can pipe through my program correctly?
推荐答案
您不应使用与fgets
和看跌
处理二进制数据。每当它看到一个新行与fgets
将停止。更糟的是,看跌
将输出额外的新行,它也将停止每当运行到一个\\ 0。使用 FREAD
和 FWRITE
代替。
You shouldn't use fgets
and puts
for dealing with binary data. fgets
will stop whenever it sees a newline. Worse, puts
will output extra newlines and it will also stop whenever it runs into a \0. Use fread
and fwrite
instead.
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