Input a special string during runtime in C

Question

In my C code I am given the following string as input:

"c:\tc\bin\a c j k.jpg"

I tried to read the input with scanf but it failed (passing the input both with and without quotation marks) and I am looking for an other solution.

My code is as follows:

char keytext[16],zzz,source[100],dest[100];
short int a;
size_t readcount;

clrscr();
printf("input the key text(max 16 characters):");
scanf("%s",&keytext);

printf("input file name:");
scanf("%s",&source);

/*fgets(source,100,stdin);
namelen=strlen(source);
if(source[namelen-1]=='\n')
source[namelen-1]='\0';*/

printf("output file name:");
scanf("%s",&dest);

Is C:\tc\bin\a c j k.jpg to be treated as a single string? — hmjd
– hmjd, Commented Sep 2, 2012 at 7:53

hmjd · Accepted Answer · 2012-09-02 08:00:18Z

1

The format specifier %s will stop consuming input when the first whitespace character is encountered, so it will only read until the end of C:\tc\bin\a. To read up to the k.jpg you can use a scanset:

char input[128];
if (1 == scanf("%127[^\n]", input))
{
}

The format specifier "%127[^\n]" means read up to the next newline character but no more than 127 characters to prevent buffer overrun. You should check the return value of scanf() before using its output, it returns the number of assignments made.

answered Sep 2, 2012 at 8:00

hmjd

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4 Comments

user1026137 Over a year ago

what about the characters \t and \b and \a in that string

hmjd Over a year ago

The are not part of a string literal, they are input so will be copied into the input array.

user1026137 Over a year ago

come on you have used sscanf on ideone and gave scanf in here, how could i come to know about that

hmjd Over a year ago

@user1026137, I had to use sscanf() on ideone as there is no way to provide input (AFAIK). However, sscanf() uses the same format specifiers as scanf(), the only difference being the source of input. See reference page for sscanf() and scanf().

fasked · Accepted Answer · 2012-09-02 08:07:57Z

0

scanf function with %s specificator expects pointer to char char *. But you pass the pointer to pointer to char char **. In order to fix it use the following code instead:

scanf("%s", keytext);
scanf("%s", source);
scanf("%s", dest);

Note, it doesn't require & symbol. If you want to read whole string with spaces, you can use fgets function.

fgets(keytext, sizeof(keytext), stdin);
fgets(source,  sizeof(source),  stdin);
fgets(dest,    sizeof(dest),    stdin);

edited Sep 2, 2012 at 8:07

answered Sep 2, 2012 at 8:00

fasked

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4 Comments

Rohan Over a year ago

But that will not solve OP question of scanning with white spaces.

user1026137 Over a year ago

@fasked if i use fgets after doing the first input using scanf, it won't work at all.

fasked Over a year ago

@user1026137 I got you! After using scanf stream keeps \n symbol. You need to clear the stream. Try to scanf("%*[^\n]") before fgets.

fasked Over a year ago

@user1026137 it seems we just don't understand your problem

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