理解 fopen 的几种参数 rwar+w+a+

Category： C++

理解

一图胜千言

截屏2023-11-05 18.18.51

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需要注意里面的a和 a+, 区别在于 a 不可以读而 a+可以读.

c - Difference between r+ and w+ in fopen() - Stack Overflow;

Mode	Read	Write	Create New File if not exist	Truncate
r	✅	❌	❌	❌
w	❌	✅	✅	✅
a	❌	✅	✅	❌
r+	✅	✅	❌	❌
w+	✅	✅	✅	✅
a+	✅	✅	✅	❌

总结:

Mode	Read	Write	Create New File if not exist	Truncate
r	✅	❌	❌	❌
w	❌	✅	✅	✅
a	❌	✅	✅	❌
r+	✅	✅	❌	❌
w+	✅	✅	✅	✅
a+	✅	✅	✅	❌

Mode	Read	Write	Create New File if not exist	Truncate
r	✅	❌	❌	❌
w	❌	✅	✅	✅
a	❌	✅	✅	❌
r+	✅	✅	❌	❌
w+	✅	✅	✅	✅
a+	✅	✅	✅	❌

Mode	Read	Write	Create New File if not exist	Truncate
r	✅	❌	❌	❌
w	❌	✅	✅	✅
a	❌	✅	✅	❌
r+	✅	✅	❌	❌
w+	✅	✅	✅	✅
a+	✅	✅	✅	❌