simple printf question

[Bint]

Hi,

I have a giant string buffer, and I want to print out small chunks of it at
a time. How do I print out, say 20 characters of a string?

Is it like this?

printf("%20s",mystring);

I can change the start point of the string, I just don't know how to tell it
to only print out X number of characters from it.
Thanks
B

 

[Richard Heathfield]

Bint said:

Hi,

I have a giant string buffer, and I want to print out small chunks of it
at
a time. How do I print out, say 20 characters of a string?

Is it like this?

printf("%20s",mystring);

I can change the start point of the string, I just don't know how to tell
it to only print out X number of characters from it.

printf("%.20s", mystring);

Note the dot in the format specifier.

Covered in K&R2 p244.

 

[Tor Rustad]

Hi,

I have a giant string buffer, and I want to print out small chunks of it at
a time. How do I print out, say 20 characters of a string?

Is it like this?

printf("%20s",mystring);

printf("%.*s", len, mystring);

 

[husterk]

Hi,

I have a giant string buffer, and I want to print out small chunks of it at
a time. How do I print out, say 20 characters of a string?

Is it like this?

printf("%20s",mystring);

I can change the start point of the string, I just don't know how to tell it
to only print out X number of characters from it.
Thanks
B

Bint,

Another more flexible method would be to snprintf() your larger string
into a temporary string buffer and then output the temporary buffer
using a standard unformatted printf(). This will allow you to
dynamically change the size of your output string by supplying a
variable length for your temporary string buffer in the snprintf()
routine (which cannot be accomplished using the "%.20s" method
described by Richard.

Keith
http://www.doubleblackdesign.com

 

[Richard Heathfield]

husterk said:

Another more flexible method would be to snprintf() your larger string
into a temporary string buffer and then output the temporary buffer
using a standard unformatted printf(). This will allow you to
dynamically change the size of your output string by supplying a
variable length for your temporary string buffer in the snprintf()
routine (which cannot be accomplished using the "%.20s" method
described by Richard.

There is really no need to go to all that trouble.

printf("%.*s\n", nchars, mystring);

Again, this is documented very clearly in K&R2.

 

[Charlie Gordon]

husterk said:



There is really no need to go to all that trouble.

printf("%.*s\n", nchars, mystring);

Again, this is documented very clearly in K&R2.

Be careful to cast nchar as (int) if it has a different type, such as
size_t.