How do I detect a "tab" character in a line of text read by fgetl?

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Clay Fulcher
Clay Fulcher 2020-5-21
回答： Clay Fulcher 2020-5-22
I am using fgetl to read lines in a text file. Is there a way to detect whether one of the whitespace characters is a "tab" ?
Thanks in advance for your help.

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采纳的回答

dpb
dpb 2020-5-21
l=fgetl(fid);
istab=(l==9); % the fast way...
%
istab=strfind(l,char(9)); % the char() string string functions way

更多回答（2 个）

Walter Roberson
Walter Roberson 2020-5-21
S = sprintf('abc\tdef'); %text with a tab in it
S == 9 %fast, simple, and tab character unlikely to change any year soon
strfind(S, sprintf('\t')) %just in case tab someday changes to a multi-character sequence
%unicode defines three additional tab-related functions
ismember(S, [0x09 0x0b 0x88 0x89 0x8a]) %HT VT CTS CTJ LTS
%unicode defines several tab symbols
ismemember(S, [0x09 0x0b 0x88 0x89 0x8a 0x2409 0x240b 0x21b9 0x21c6 0x21E4 0x21E5]) %HT VT CTS CTJ LTS various tab symbols
Clay Fulcher
Clay Fulcher 2020-5-22
Thanks to Walter Roberson and dpb for the help above. Here is the new "tab detector!"
function [x, tabpositions] = istab(line)
%
% This function detects any "tab" characters in a character string and
% returns logical TRUE if tabs are present, or logical FALSE if tabs are
% not present. Optionally returns the positions of the tab(s) in the line.
%
% USAGE
% [x,tabpositions]=istab(line)
%
% INPUT
% line - [1 x n] character string with or without tabs
%
% OUTPUT
% x - logical TRUE or FALSE indicating presence of tab(s) in line.
% tabpositions - [1 x ntabs] vector showing positions of tabs in line.
%
% line must be a character string or empty
if ~ischar(line) & ~isempty(line)
disp(' ')
disp(' Input must be a character string.')
return
end
% line must contain only one line
if size(line,1)>1
disp(' ')
error(' Character string must be no more than one line.' )
return
end
% Put logical 1 where tab exists, logical 0 where it does not in string.
% Could use x=(line==9), but the following eliminates the case where this
% designator for the tab character is changed in the future.
x=(line==sprintf('\t'));
% Find the positions in line where tabs exist.
tabpositions=find(x);
if isempty(tabpositions), tabpositions=[]; end
% Return only logical 1 or 0, however many tabs there are in line.
x=x(find(x));
if ~isempty(x), x=x(1); end
if isempty(x), x=logical(0); end
% Display the logical result for tab existence.
if x, 1==1, end
if ~x, 1==2, end
return

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