如何shell命令的输出分配给C语言的变量 [英] How to assign shell command output to a variable in C language

问题描述

我要的shell命令的输出（无回音| grep的纪念品| awk的'{打印$ 2} ）收集在一个变量，这样我可以用它C程序。所以，我有code在这里。

I want the output of the shell command (echo free | grep Mem| awk '{print $2}') collected in a variable so that I can use it in a C program. So I have the code here.

 system("TOTAL=$(echo `free | grep Mem| awk '{print $2}'`)");
 popen("grep -v procs $1 | grep -v free | awk '{USED=TOTAL-$4-$5-$6;print USED}'", "r");

我可以使用同样的程序中的变量TOTAL一个的popen（）调用中，如上图所示？

Can I use the variable TOTAL in the same program inside a popen() call as shown above ?

推荐答案

您需要创建一个包含您要运行完整的脚本中的字符串，或者您需要创建一个可以简单地运行一个脚本，然后安排与的popen读取脚本输出（）。无论是可能的;哪一个更容易取决于你的脚本技能水平与你的C ++编程技巧。

You will need to create a string which contains the complete script that you want run, or you will need to create a script which can be run simply, and then arrange to read the output of that script with popen(). Either is possible; which is easier depends on the level of your scripting skills vs your C programming skills.

char command[4096];

strcpy(command, "TOTAL=$(free | grep Mem| awk '{print $2}')\n");
strcat(command, "grep -v procs $1 | grep -v free |\n");
strcat(command, "awk '{USED=TOTAL-$4-$5-$6;print USED}' TOTAL=$TOTAL\n");

FILE *in = popen(command, "r");

...read the results, etc...

的字符串操作简化了第一个shell脚本，然后通过计算 AWK 总量的值。

其他的方式做这将是读免费的输出| grep的纪念品| AWK'{打印$ 2} - 这是总价值 - 从一个使用的popen（），那么构建值到第二个命令

The other way to do it would be to read the output from free | grep Mem | awk '{print $2}' - the value that is TOTAL - from one use of popen(), then build that value into the second command:

char command[4096];

strcpy(command, "free | grep Mem| awk '{print $2}'");
char total[20];
FILE *in1 = popen(command, "r");
...read TOTAL into total...

strcpy(command, "grep -v procs $1 | grep -v free |\n");
strcat(command, "awk '{USED=TOTAL-$4-$5-$6;print USED}' TOTAL=");
strcat(command, total);

FILE *in2 = popen(command, "r");

这篇关于如何shell命令的输出分配给C语言的变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！