C语言中可用的标准预定义宏__FILE__显示文件的完整路径。有办法缩短这条路吗?我的意思是
/full/path/to/file.c
我看到
to/file.c
or
file.c
当前回答
#include <algorithm>
#include <string>
using namespace std;
string f( __FILE__ );
f = string( (find(f.rbegin(), f.rend(), '/')+1).base() + 1, f.end() );
// searches for the '/' from the back, transfers the reverse iterator
// into a forward iterator and constructs a new sting with both
其他回答
下面是一个适用于Linux(路径'/')和Windows('\'和'/'混合)的可移植函数。使用gcc, clang和vs编译。
#include <string.h>
#include <stdio.h>
const char* GetFileName(const char *path)
{
const char *name = NULL, *tmp = NULL;
if (path && *path) {
name = strrchr(path, '/');
tmp = strrchr(path, '\\');
if (tmp) {
return name && name > tmp ? name + 1 : tmp + 1;
}
}
return name ? name + 1 : path;
}
int main() {
const char *name = NULL, *path = NULL;
path = __FILE__;
name = GetFileName(path);
printf("path: %s, filename: %s\n", path, name);
path ="/tmp/device.log";
name = GetFileName(path);
printf("path: %s, filename: %s\n", path, name);
path = "C:\\Downloads\\crisis.avi";
name = GetFileName(path);
printf("path: %s, filename: %s\n", path, name);
path = "C:\\Downloads/nda.pdf";
name = GetFileName(path);
printf("path: %s, filename: %s\n", path, name);
path = "C:/Downloads\\word.doc";
name = GetFileName(path);
printf("path: %s, filename: %s\n", path, name);
path = NULL;
name = GetFileName(NULL);
printf("path: %s, filename: %s\n", path, name);
path = "";
name = GetFileName("");
printf("path: %s, filename: %s\n", path, name);
return 0;
}
标准输出:
path: test.c, filename: test.c
path: /tmp/device.log, filename: device.log
path: C:\Downloads\crisis.avi, filename: crisis.avi
path: C:\Downloads/nda.pdf, filename: nda.pdf
path: C:/Downloads\word.doc, filename: word.doc
path: (null), filename: (null)
path: , filename:
Try
#include <string.h>
#define __FILENAME__ (strrchr(__FILE__, '/') ? strrchr(__FILE__, '/') + 1 : __FILE__)
对于Windows，使用“\\”而不是“/”。
#include <algorithm>
#include <string>
using namespace std;
string f( __FILE__ );
f = string( (find(f.rbegin(), f.rend(), '/')+1).base() + 1, f.end() );
// searches for the '/' from the back, transfers the reverse iterator
// into a forward iterator and constructs a new sting with both
c++ 11 msvc2015u3、gcc5.4 clang3.8.0 模板<typename T, size_t S> (const T (& str)[S]， size_t i = S - 1) ｛ 返回(str[i] == '/' || str[i] == '\\') ?I + 1:(I > 0 ?Get_file_name_offset (str, I - 1): 0); ｝ template <typename T> (T (& str)[1]) ｛ 返回0; ｝
'
int main()
{
printf("%s\n", &__FILE__[get_file_name_offset(__FILE__)]);
}
代码在以下情况下产生编译时偏移量:
gcc:至少gcc6.1 + -O1 Msvc:将结果放入constexpr变量: constexpr auto file = &__FILE__[get_file_name_offset(__FILE__)]; printf (" % s \ n ",文件); Clang:坚持不编译时计算
有一个技巧可以强制所有3个编译器进行编译时间计算，即使在调试配置中禁用优化:
namespace utility {
template <typename T, T v>
struct const_expr_value
{
static constexpr const T value = v;
};
}
#define UTILITY_CONST_EXPR_VALUE(exp) ::utility::const_expr_value<decltype(exp), exp>::value
int main()
{
printf("%s\n", &__FILE__[UTILITY_CONST_EXPR_VALUE(get_file_name_offset(__FILE__))]);
}
https://godbolt.org/z/u6s8j3
纯粹的编译时解决方案。它基于这样一个事实:字符串字面量的sizeof()返回其长度+1。
#define STRIPPATH(s)\
(sizeof(s) > 2 && (s)[sizeof(s)-2] == '/' ? (s) + sizeof(s) - 1 : \
sizeof(s) > 3 && (s)[sizeof(s)-3] == '/' ? (s) + sizeof(s) - 2 : \
sizeof(s) > 4 && (s)[sizeof(s)-4] == '/' ? (s) + sizeof(s) - 3 : \
sizeof(s) > 5 && (s)[sizeof(s)-5] == '/' ? (s) + sizeof(s) - 4 : \
sizeof(s) > 6 && (s)[sizeof(s)-6] == '/' ? (s) + sizeof(s) - 5 : \
sizeof(s) > 7 && (s)[sizeof(s)-7] == '/' ? (s) + sizeof(s) - 6 : \
sizeof(s) > 8 && (s)[sizeof(s)-8] == '/' ? (s) + sizeof(s) - 7 : \
sizeof(s) > 9 && (s)[sizeof(s)-9] == '/' ? (s) + sizeof(s) - 8 : \
sizeof(s) > 10 && (s)[sizeof(s)-10] == '/' ? (s) + sizeof(s) - 9 : \
sizeof(s) > 11 && (s)[sizeof(s)-11] == '/' ? (s) + sizeof(s) - 10 : (s))
#define __JUSTFILE__ STRIPPATH(__FILE__)
请随意将条件操作符级联扩展到项目中最大的合理文件名。路径长度并不重要，只要检查距离字符串的末尾足够远。
我将看看我是否可以得到一个类似的宏，没有硬编码的长度与宏递归…
