`readlines`

Reads the lines of a text file into a string array.

Category: Data Import and Analysis > Data Import and Export

Syntax

lines = readlines(filename)

Returns one string per line, as a column.

Description

This is the shortest way to loop over the lines of a file: for ln = readlines(f)'. Because the result is a string array, you can use contains, startsWith, split and str2double on all lines at once.

Input arguments

filename: Name of a text file.

Output arguments

lines: Column string array, one element per line, without line terminators.

Example

Filter lines

fid = fopen('log.txt', 'w');
fprintf(fid, 'ok 1\nerror 2\nok 3\nerror 4');
fclose(fid);
L = readlines('log.txt')
L(startsWith(L, 'error'))

Output

L = 4×1 string array

    "ok 1"
    "error 2"
    "ok 3"
    "error 4"
ans = 2×1 string array

    "error 2"
    "error 4"

Notes

When the file ends with a newline, the result includes a final empty string.

readlines