Linux system 函式返回值
阿新 • • 發佈：2019-01-31
如何判斷階段2中，shell指令碼是否正常執行結束呢？系統提供了巨集：WIFEXITED(status)。如果WIFEXITED(status)為真，則說明正常結束。
如何取得階段3中的shell返回值？你可以直接通過右移8bit來實現，但安全的做法是使用系統提供的巨集：WEXITSTATUS(status)。
由於我們一般在shell指令碼中會通過返回值判斷本指令碼是否正常執行，如果成功返回0，失敗返回正數。
所以綜上，判斷一個system函式呼叫shell指令碼是否正常結束的方法應該是如下3個條件同時成立：
（1）-1 != status
（2）WIFEXITED(status)為真
（3）0 == WEXITSTATUS(status)
WIFEXITED(stat_val) Evaluates to a non-zero value if status was returned for a child process that terminated normally.
WEXITSTATUS(stat_val) If the value of WIFEXITED(stat_val) is non-zero, this macro evaluates to the low-order 8 bits of the status argument that the child process passed to _exit() or exit(), or the value the child process returned from main().
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
int main()
{
pid_t status;
status = system("./test.sh");
if (-1 == status)
{
printf("system error!");
}
else
{
printf("exit status value = [0x%x]\n", status);
if (WIFEXITED(status))
{
if (0 == WEXITSTATUS(status))
{
printf("run shell script successfully.\n");
}
else
{
printf("run shell script fail, script exit code: %d\n", WEXITSTATUS(status));
}
}
else
{
printf("exit status = [%d]\n", WEXITSTATUS(status));
}
}
return 0;
} WIFEXITED(stat_val) Evaluates to a non-zero value if status was returned for a child process that terminated normally.
WEXITSTATUS(stat_val) If the value of WIFEXITED(stat_val) is non-zero, this macro evaluates to the low-order 8 bits of the status argument that the child process passed to _exit() or exit(), or the value the child process returned from main().