c - Does '\0' appear naturally in text files? -


i encountered annoying bug today string (stored char[]) printed junk @ end. string suppose printed (using arduino print/write functions) correct (it correctly included \r , \n). however, there junk printed @ end.

i allocated element store '\0' after '\r' , '\n' (which last 2 characters in string printed). then, print() printed string correctly. seems '\0' used indicate print() function string had terminated (i remember reading in kernighan's c).

this bug appeared in code reads text file. occurred me did not encounter '\0' @ when designed code. leads me believe '\0' has no practical use in text editors , merely used print functions. correct?

c strings terminated nul byte ('\0') - implicitly appended string literals in double quotes, , used terminator standard library functions operating on strings. follows c strings can not contain '\0' terminator in between other characters, since there no way tell whether actual end of string or not.

(of course handle strings in c language other c strings - e.g., adding integer record length of string make terminator unnecessary, such strings not interoperable functions expecting c strings.)

a "text file" in general not governed c standard, , user of c program conceivably give file containing nul byte input c program (which unable handle "correctly" above reasons if read file c strings). however, nul byte has no valid reason existing in plain text file, , may considered @ least de facto standard text files not contain nul byte (or other control characters, might break transmission of text through terminals or serial protocols).

i argue acceptable (though not necessary!) limitation program working on plain text input not guarantee correct output if there nul bytes in input. however, programmer should aware of possibility regardless of whether treated correctly, , not allow cause undefined behaviour in program. user input, should considered "unsafe" in sense can contain (e.g., maliciously formed on purpose).


Comments

Post a Comment

Popular posts from this blog

c# - Validate object ID from GET to POST -

i have method allows user access comment have made on site. have post method lets them update comment. my normal solution send entire comment model through, let them update it, update on database when post back. involve sending commentid through in hiddenfor , can manipulated. how can verify commentid sent in get method same i'm getting in post , not able alter comment wish? how can verify commentid sent in method same i'm getting in post? basically have validate following things in post - user logged-in user. authenticated users post comments. commentid in post , should valid commentid , should present in database. userid associated logged-in user should same userid associated comment . comment should contain userid column, can check @ time of update. to make sure update happens comment has been sent in get - hold commentid in session , in post action compare commentid value in session .
Read more

node.js - Custom Model Validator SailsJS -

when using custom model validator checks record within model. return within spread doesn't seem end control flow. //post.js model /** * custom validator **/ types: { isuservalid: function(user_id) { var promise = require('bluebird'); promise.all([ user.findone({id: user_id}) ]) .spread(function(user) { console.log(user); if (user === null || user === undefined) { console.log('failed'); return false; }else{ console.log('passed'); return true; } }); } }, my response standard validation failed response. { "error": "e_validation", "status": 400, "summary": "1 attribute invalid", "model": "post", "invalidattributes": { "owner": [ { "rule": "isuservalid", ...
Read more

php - Find a regex to take part of Email -

i have following emails need extract part from: bestellnummer xxx: 1 von xxx, 1er pack ------------- anfang der nachricht ------------- foo bar baz foo bar baz // <<<<< need text here ------------- ende der nachricht ------------- ------------- anfang der nachricht ------------- foo bar baz foo bar baz ------------- ende der nachricht ------------- there 0 unlimited occurences of ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- and i'm able extract first part regex: $re = "/------------- .*? -------------.?(.*?).?------------- .*? -------------/s"; but, i'm quite new on learning regex, i'm pretty sure there must better regex extract part (foo bar baz foo bar baz) of text between ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- as can in different languages, i'm using .? to match between hyphens. i...
Read more