Read data from text file (2024)

Read data from text file

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A = fscanf(fileID,formatSpec)

A = fscanf(fileID,formatSpec,sizeA)

[A,count]= fscanf(___)



A = fscanf(fileID,formatSpec) readsdata from an open text file into column vector A andinterprets values in the file according to the format specified by formatSpec.The fscanf function reapplies the format throughoutthe entire file and positions the file pointer at the end-of-filemarker. If fscanf cannot match formatSpec tothe data, it reads only the portion that matches and stops processing.

The text file is indicated by the file identifier, fileID.Use fopen to open the file, specify the characterencoding, and obtain the fileID value. When youfinish reading, close the file by calling fclose(fileID).


A = fscanf(fileID,formatSpec,sizeA) readsfile data into an array, A, with dimensions, sizeA,and positions the file pointer after the last value read. fscanf populates A incolumn order. sizeA must be a positive integeror have the form [m n], where m and n arepositive integers.


[A,count]= fscanf(___) additionally returns the numberof fields that fscanf reads into A.For numeric data, this is the number of values read. You can use thissyntax with any of the input arguments of the previous syntaxes.


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Read File Contents into Column Vector

Open Live Script

Create a sample text file that contains floating-point numbers.

x = 100*rand(8,1);fileID = fopen('nums1.txt','w');fprintf(fileID,'%4.4f\n',x);fclose(fileID);

View the contents of the file.

type nums1.txt

Open the file for reading, and obtain the file identifier, fileID.

fileID = fopen('nums1.txt','r');

Define the format of the data to read. Use '%f' to specify floating-point numbers.

formatSpec = '%f';

Read the file data, filling output array, A, in column order. fscanf reapplies the format, formatSpec, throughout the file.

A = fscanf(fileID,formatSpec)
A = 8×1 81.4724 90.5792 12.6987 91.3376 63.2359 9.7540 27.8498 54.6882

A is a column vector containing data from the file.

Close the file.


Read File Contents into Array

Open Live Script

Create a sample text file that contains integers and floating-point numbers.

x = 1:1:5;y = [x;rand(1,5)];fileID = fopen('nums2.txt','w');fprintf(fileID,'%d %4.4f\n',y);fclose(fileID);

View the contents of the file.

type nums2.txt
1 0.81472 0.90583 0.12704 0.91345 0.6324

Open the file for reading, and obtain the file identifier, fileID.

fileID = fopen('nums2.txt','r');

Define the format of the data to read and the shape of the output array.

formatSpec = '%d %f';sizeA = [2 Inf];

Read the file data, filling output array, A, in column order. fscanf reuses the format, formatSpec, throughout the file.

A = fscanf(fileID,formatSpec,sizeA)
A = 2×5 1.0000 2.0000 3.0000 4.0000 5.0000 0.8147 0.9058 0.1270 0.9134 0.6324

Transpose the array so that A matches the orientation of the data in the file.

A = A'
A = 5×2 1.0000 0.8147 2.0000 0.9058 3.0000 0.1270 4.0000 0.9134 5.0000 0.6324

Skip Specific Characters in File

Skip specific characters in a sample file,and return only numeric data.

Create a sample text file containing temperature values.

str = '78°C 72°C 64°C 66°C 49°C';fileID = fopen('temperature.dat','w');fprintf(fileID,'%s',str);fclose(fileID);

Read the numbers in the file, skipping the text, °C.Also return the number of values that fscanf reads.The extended ASCII code 176 represents the degree sign.

fileID = fopen('temperature.dat','r');degrees = char(176);[A,count] = fscanf(fileID, ['%d' degrees 'C'])fclose(fileID);
A = 78 72 64 66 49count = 5

A is a vector containing the numeric valuesin the file. count indicates that fscanf readfive values.

Input Arguments

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fileIDFile identifier

File identifier of an open text file, specified as an integer.Before reading a file with fscanf, you must use fopen toopen the file and obtain the fileID.

Data Types: double

formatSpecFormat of data fields
character vector | string scalar

Format of the data fields in the file, specified as a charactervector or string scalar of one or more conversion specifiers. When fscanf readsa file, it attempts to match the data to the format specified by formatSpec.

Numeric Fields

This table lists available conversion specifiers for numericinputs. fscanf converts values to their decimal(base 10) representation.

Numeric Field TypeConversion SpecifierDetails

Integer, signed


Base 10


The values in the file determine the base:

  • The default is base 10.

  • If the initial digits are 0x or 0X,then the values are hexadecimal (base 16).

  • If the initial digit is 0, thenvalues are octal (base 8).

%ld or %li

64-bit values, base 10, 8, or 16

Integer, unsigned


Base 10


Base 8 (octal)


Base 16 (hexadecimal)

%lu, %lo, %lx

64-bit values, base 10, 8, or 16

Floating-point number


Floating-point fields can containany of the following (not case sensitive): Inf, -Inf, NaN,or -NaN.



Character Fields

This table lists available conversion specifiers for characterinputs.

Character Field TypeConversion SpecifierDescription

Character vector or string scalar


Read all characters excluding white spaces.


Read any single character, including white space.
Toread multiple characters at a time, specify field width.



Read only characters in the brackets up to the firstnonmatching character or white space.

Example: %[mus] reads 'summer' as 'summ'.

If formatSpec contains a combination of numericand character specifiers, then fscanf convertseach character to its numeric equivalent. This conversion occurs evenwhen the format explicitly skips all numeric values (for example, formatSpec is '%*d%s').

Optional Operators

  • Fields and Characters to Ignore

    fscanf reads all numeric values and charactersin your file in sequence, unless you tell it to ignore a particularfield or a portion of a field. To skip fields, insert an asterisk (*) after the percent sign (%).For example, to skip integers, specify %*d.

  • Field Width

    To specify the maximum number of digits or text characters toread at a time, insert a number after the percent character. For example, %10c readsup to 10 characters at a time, including white space. %4f readsup to 4 digits at a time, including the decimal point.

  • Literal Text to Ignore

    fscanf ignores specified text appended tothe formatSpec conversion specifier.

    Example: Level%u reads 'Level1' as 1.

    Example: %uStep reads '2Step' as 2.

sizeADimensions of output array
Inf (default) | integer | two-element row vector

Dimensions of the output array, A, specifiedas Inf, an integer, or a two-element row vector.

Form of the sizeA InputDescription
InfRead to the end of the file.
For numeric data,the output, A, is a column vector.
Fortext data, A is a character vector.
nRead at most n numeric values orcharacter fields.
For numeric data, the output, A,is a column vector.
For text data, A,is a character vector.
[m,n]Read at most m*n numericvalues or character fields. n can be Inf,but m cannot. The output, A,is m-by-n, filled in columnorder.

Output Arguments

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A — File data
column vector | matrix | character vector | character array

File data, returned as a column vector, matrix, character vectoror character array. The class and size of A dependon the formatSpec input:

  • If formatSpec contains only numericspecifiers, then A is numeric. If you specify the sizeA argument,then A is a matrix of the specified size. Otherwise, A isa column vector. If the input contains fewer than sizeA values,then fscanf pads A with zeros.

    • If formatSpec contains only 64-bitsigned integer specifiers, then A is of class int64.

    • If formatSpec contains only 64-bitunsigned integer specifiers, then A is of class uint64.

    • Otherwise, A is of class double.

  • If formatSpec contains only characteror text specifiers (%c or %s),then A is a character array. If you specify sizeA andthe input contains fewer characters, then fscanf pads A with char(0).

  • If formatSpec contains a combinationof numeric and character specifiers, then A isnumeric, of class double, and fscanf convertseach text characters to its numeric equivalent. This occurs even when formatSpec explicitlyskips all numeric fields (for example, formatSpec is '%*d%s').

  • If MATLAB® cannot match the file data to formatSpec,then A can be numeric or a character array. Theclass of A depends on the values that fscanf readsbefore it stops processing.

count — Number of characters read

Number of characters read, returned as a scalar value.


  • Format specifiers for the reading functions sscanf and fscanf differfrom the formats for the writing functions sprintf and fprintf.The reading functions do not support a precision field. The widthfield specifies a minimum for writing but a maximum for reading.


MATLAB reads characters using the encoding scheme associatedwith the file. You specify the encoding when you open the file usingthe fopen function.

Extended Capabilities

Version History

Introduced before R2006a

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This function supports thread-based environments.

See Also

fopen | fprintf | textscan | sscanf | fgetl | fgets | fread


  • Import Text Data Files with Low-Level I/O

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Read data from text file (1)

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Read data from text file (2024)
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