how to remove values based on space delimiter

the values present in my file is

f 1 2 3

f 1 2 3

f 1 2 3 4

f 2 3 4

f 4 5 6 7

i have to read every line and check for 4 values separated by space

ie f 1 2 3

if that line has 5 values the last value should get removed

ie

my output should be

f 1 2 3

f 1 2 3

f 1 2 3 

f 2 3 4

f 4 5 6

does any built in is there ..pls help....thanks in advance

Answer 1

[Walter Roberson]

S = fileread('YourFileName.txt');  %read file

NewS = regexprep(S, '(?m)(?-s)^(\w+\s+\w+\s+\w+).*', '$1');  %do edit

fid = fopen('YourNewFile.txt, 'wt');  %write out new version
fwrite(fid, NewS);
fclose(fid);

[Sharen H]

thanks a lot...

[Sharen H]

if the values are like this

f 1\2 2\3 2\4 4\5

what changes should i ,make

[Walter Roberson]

'(?m)(?-s)^(\w+\s+[0-9\\]+\s+[0-9\\]+).*'

This presumes that the first thing on the line will not be of the same form, and that the other values only have digits and backslash.