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ftell

Current position

Syntax

position = ftell(fileID)

Description

example

position = ftell(fileID) returns the current location of the position pointer in the specified file.

  • If the query is successful, then position is a zero-based integer that indicates the number of bytes from the beginning of the file.

  • If the query is unsuccessful, then position is -1.

Examples

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When you open a file, MATLAB® creates a pointer to indicate the current position within the file. Open the following badpoem.txt file and perform a read operation (which advances the position pointer). Then, query the final position in the file after the read operation.

Use fopen to open the file. Then, use ftell to query the current position.

fid = fopen('badpoem.txt');
ftell(fid)
ans = 0

Using fgetl, read the first line and examine the current position after the read operation.

tline1 = fgetl(fid)  % read the first line 
tline1 = 
'Oranges and lemons,'
ftell(fid)
ans = 20

Read the second line and examine the current position.

tline2 = fgetl(fid)  % read the second line 
tline2 = 
'Pineapples and tea.'
ftell(fid)
ans = 40

Close the file.

fclose(fid);

Input Arguments

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File identifier of an open file, specified as an integer. To open a file and obtain its valid identifier use the fopen function.

Data Types: double

Extended Capabilities

Introduced before R2006a

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