Take input string in c

Question

To take input string in c, we can opt for 2 ways(as per my knowledge please add more if i missing something)

char name[10];
scanf(" %s",name); // First case
scanf("%[\n]s",name); // Second case

1st one will consider the string till the first blank space and 2nd will take complete sentence till the new line break as a string but to take input we need to improvise the 2nd statement as

scanf(" %[\n]s",name);

my question is what is extra spacing doing here ? because sometime my compiler will behave normally even if i will remove the 's' from scanf statement and without extra spacing before '%' but sometime it wont work.

Why do people ask questions that can be answered simply by reading the documentation? — Barmar, May 01 '16 at 09:57
@nishant-kumar : I wonder the `s` at the end of `%[\n]s` makes a difference. — sjsam, May 01 '16 at 10:03
http://stackoverflow.com/questions/17079144/why-we-need-to-put-space-before-c Read the answer — sentientmachine, May 01 '16 at 10:05
http://stackoverflow.com/questions/8177752/scanf-ns-a-vs-getsa — user3078414, May 01 '16 at 10:06
Possible duplicate of [What does space in scanf mean?](http://stackoverflow.com/questions/6582322/what-does-space-in-scanf-mean) — stijn, May 01 '16 at 10:46
There are differences and problems with both. The more robust approach is to use neither. Use `fgets()`. — chux - Reinstate Monica, May 02 '16 at 14:49
"sometime it wont work." is not that useful. Posting input, output and expected output is useful. — chux - Reinstate Monica, May 02 '16 at 15:01

score 1 · Answer 1 · edited May 02 '16 at 20:10

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The space before the % operator will make it so that any white-space before the entered string is removed as well as whatever effect the format specifiers after the % operator have on the input.

Ex: "\n\t Hello World" entered with " %[^\n]" will be recorded as "Hello World".

edited May 02 '16 at 20:10

chux - Reinstate Monica

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answered May 01 '16 at 14:50

William Gerecke

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Disagree with "The spacing will do nothing ..." . The space in the format `scanf(" %[\n]s",name);` has an important impact: consume leading white-space. – chux - Reinstate Monica May 02 '16 at 14:52
@chux Remove or create whitespace? – William Gerecke May 02 '16 at 16:46
"Remove or create whitespace?" is unclear as `scanf()` does not create white-space. Perhaps re-phrase the question. – chux - Reinstate Monica May 02 '16 at 17:03
@chux Sorry, I meant to ask what you meant by "consume whitespace". If you can clarify, I will change my answer. – William Gerecke May 02 '16 at 17:23
A `scanf()` white-space directive like `" "` consumes whitespace from `stdin`. White-spaces characters are read, but not save anywhere. This is often important before `"%[\n]"` to consume a previous entry's line-feed. – chux - Reinstate Monica May 02 '16 at 17:35
So, to clarify... With the space, all whitespace from the input would b deleted so "hello world" would become "helloworld"?@chux – William Gerecke May 02 '16 at 17:57
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Not quite. With the space, all _leading_ white-space from the input would be consumed before specifier `"%[^\n]"`. Input `"\n\t hello world"` be saved as "hello world" in `name[]`. – chux - Reinstate Monica May 02 '16 at 19:50
Okay @chux, Thank you for this. I will revise my answer. This is information that I did not know earlier. – William Gerecke May 02 '16 at 19:53
when i am not putting space it is not taking input and printing some symbols, but after putting space it is working fine in my dev c compiler – Nishant Kumar May 03 '16 at 18:02

score 0 · Answer 2 · edited Sep 11 '16 at 12:40

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If white space character is left in first input stream and mistakenely read by next input scanf: to delete the white space character from input stream either use space before format string or use fflush (stdin) function.

edited Sep 11 '16 at 12:40

YakovL

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answered Sep 11 '16 at 11:56

pallvi goel

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Take input string in c

2 Answers2