Analysis of File open mode (r/w/a/r+/w+/a+/rb/wb/ab/rb+/wb+/ab+) in C language

Analysis of open mode of C language file

In the C language file manipulation syntax, open file files have the following 12 modes, such as:

open Mode	can only read	can only write		read Write both
text mode	R	W	a	r+	w+	A +
binary mode	RB	WB	AB	rb+ (r+b)	wb+ (w+b)	ab+ (a+b)

The binary mode is similar to the text mode operation, except that it is read and write in the form of a binary stream, the following is an example of text mode :

1."R" mode :

1.1 Open file for " Read Only " operation, that is, the content can only be read from the file.

1.2 If the file you want to manipulate does not exist, the open fails .

1.3 When the file is successfully opened, the file pointer is at the beginning of the file.

1.4 When you open a file, the original content in the file is not emptied .

1.5 The content can be read from anywhere in the file.

2."W" mode :

2.1 Open file for " write only " operation, that is, the content can only be written to the file.

2.2 If the file you want to manipulate does not exist, create a new file .

2.3 When the file is successfully opened, the file pointer is at the beginning of the file.

2.4 When the file is opened, the original contents of the file are emptied .

2.5 can write to any location in the file, and when the write operation, the contents of the original location will be overwritten .

3."A" mode :

3.1 Open the file for an " append " operation, that is, you can only write to the file.

3.2 If the file you want to manipulate does not exist, create a new file .

3.3 When the file is successfully opened, the file pointer is at the end of the file.

3.4 When you open a file, the original content in the file is not emptied .

3.5 can append (write) content to the end of the file only.

4."r+" mode :

4.1 Open the file for " Read and write " operation, that is both readable and writable.

4.2 If the file you want to manipulate does not exist, the open fails .

4.3 When the file is successfully opened, the file pointer is at the beginning of the file.

4.4 When you open a file, the original content in the empty text is not cleared .

4.5 Whether the content is read or written, can be anywhere in the file, and write operations, will overwrite the original location of the content.

5."w+" mode :

5.1 Open the file for " Read and write " operation, that is both readable and writable.

5.2 If the file you want to manipulate does not exist, create a new file .

5.3 When the file is successfully opened, the file pointer is at the beginning of the file.

5.4 When the file is opened, the original contents of the file are emptied .

5.5 Whether the content is read or written, can be anywhere in the file, and write operations, will overwrite the original location of the content.

6."A +" mode :

6.1 Open the file for " Read and write " operation, that is both readable and writable.

6.2 If the file you want to manipulate does not exist, create a new file .

6.3 When the file is successfully opened, the file pointer is at the end of the file.

6.4 When you open a file, the original content in the file is not emptied .

6.5 When the content is read, it can be done anywhere , but when the content is written, it is appended only to the end of the file.

Attached form to strengthen memory:

Open mode	Briefly	If you want to operate the File does not exist	After the file is successfully opened File pointer location	Whether to empty Original content	Read location	Write location	Note
R	Read-only	Open failed	Beginning	Whether	Any position read	Not writable	-
W	Write only	New	Beginning	Is	Non-readable	Write Anywhere	Overwrite original location content when writing
a		new	end	no	cannot read
r+	Write	Open failed	Beginning	Whether	Any position read	Write Anywhere	Overwrite original location content when writing
w+		new	Start	is	anywhere read	write   anywhere,	overwrites the original location content
A +		New	End	Whether	Any position read	only Tail Write	-

Different open modes correspond to different operating modes and need to be carefully planned for use.

Analysis of File open mode (r/w/a/r+/w+/a+/rb/wb/ab/rb+/wb+/ab+) in C language