-b FILE
              FILE exists and is block special
       -c FILE
              FILE exists and is character special
       -d FILE
              FILE exists and is a directory
       -e FILE
              FILE exists
       -f FILE
              FILE exists and is a regular file
       -g FILE
              FILE exists and is set-group-ID
       -G FILE
              FILE exists and is owned by the effective group ID
       -h FILE
              FILE exists and is a symbolic link (same as -L)
       -k FILE
              FILE exists and has its sticky bit set
       -L FILE
              FILE exists and is a symbolic link (same as -h)
       -O FILE
              FILE exists and is owned by the effective user ID
       -p FILE
              FILE exists and is a named pipe
       -r FILE
              FILE exists and read permission is granted
       -s FILE
              FILE exists and has a size greater than zero
       -S FILE
              FILE exists and is a socket
       -t FD  file descriptor FD is opened on a terminal
       -u FILE
              FILE exists and its set-user-ID bit is set
       -w FILE
              FILE exists and write permission is granted
       -x FILE
              FILE exists and execute (or search) permission is granted

1. test命令

它经常用来测试条件表达式，用到的命令为test -e <文件>。



2. 用bash shell检查

假设我们有文件目录/home/benben/go_project和文件/home/benben/go_project/test.txt，下面我们用bash shell命令来检测下这个目录和文件是否存在。


检查目录，执行命令[-d /home/benben/go_project ] && echo "found" || echo "not found"或者[-d ./go_project ] && echo "found" || echo "not found"。
检查文件，执行命令[-f /home/benben/go_project/test.txt ] && echo "found" || echo "not found"或者[-f ./test.txt ] && echo "found" || echo "not found"

一、access函数
功能描述： 
检查调用进程是否可以对指定的文件执行某种操作。 
  
用法： 
#include <unistd.h>
#include <fcntl.h>

int access(const char *pathname, int mode);   
  
参数： 
pathname: 需要测试的文件路径名。   
mode: 需要测试的操作模式，可能值是一个或多个R_OK(可读?), W_OK(可写?), X_OK(可执行?) 或 F_OK(文件存在?)组合体。 
  
返回说明： 
成功执行时，返回0。失败返回-1，errno被设为以下的某个值 
EINVAL： 模式值无效   
EACCES： 文件或路径名中包含的目录不可访问 
ELOOP ： 解释路径名过程中存在太多的符号连接 
ENAMETOOLONG：路径名太长 
ENOENT：  路径名中的目录不存在或是无效的符号连接 
ENOTDIR： 路径名中当作目录的组件并非目录 
EROFS： 文件系统只读 
EFAULT： 路径名指向可访问的空间外 
EIO：  输入输出错误 
ENOMEM： 不能获取足够的内核内存 
ETXTBSY：对程序写入出错
 
#include <stdio.h>   
#include <stdlib.h>   
#include <unistd.h>   
#include <fcntl.h>   
  
int main()   
{   
    if((access("test.c",F_OK))!=-1)   
    {   
        printf("文件 test.c 存在.\n");   
    }   
    else  
    {   
        printf("test.c 不存在!\n");   
    }   
  
    if(access("test.c",R_OK)!=-1)   
    {   
        printf("test.c 有可读权限\n");   
    }   
    else  
    {   
        printf("test.c 不可读.\n");   
    }   
  
    if(access("test.c",W_OK)!=-1)   
    {   
        printf("test.c 有可写权限\n");   
    }   
    else  
    {   
        printf("test.c 不可写.\n");   
    }   
    if(access("test.c",X_OK)!=-1)   
    {   
        printf("test.c 有可执行权限\n");   
    }   
    else  
    {   
        printf("test.c 不可执行.\n");   
    }   
  
    return 0;   
}  
 
#include <stdio.h>   
#include <time.h>   
int main()   
{   
    time_t now = time(NULL);   
    char buf[25];   
    strftime(buf,24,"%Y%m%d",localtime(&now));   
    printf("%s\n",buf);   
  
    strftime(buf,24,"%Y-%m-%d %H:%M:%S",localtime(&now));   
    printf("%s\n",buf);   
  
    strftime(buf,24,"%y%m%d %H:%M:%S",localtime(&now));   
    printf("%s\n",buf);   
  
    strftime(buf,24,"%y%m%d",localtime(&now));   
    printf("%s\n",buf);   
  
    strftime(buf,24,"%H:%M:%S",localtime(&now));   
    printf("%s\n",buf);   
    return 0;   
}  

 

用access函数
access的第一个参数是文件路径，第二个参数是测试的模式。常用的有R_OK:测试读权限，W_OK:测试写权限，X_OK:测试执行权限，F_OK:测试文件是否存在;