how to cantenate strings in C

[Helen]

Hi there

I am planning to
open a lot of files name test1.txt, test2.txt ...
But I don't know how to change integer to be string
like 1 to char'1' and cantenate them with test and .txt

thanks a lot!

 

[Aggro]

Hi there

I am planning to
open a lot of files name test1.txt, test2.txt ...
But I don't know how to change integer to be string
like 1 to char'1' and cantenate them with test and .txt

/* Make sure you have enough room in your result char array. */
char result[100];

int filenumber = 10;

sprintf( result, "%s%d.txt", "filename", filenumber );
printf( "%s\n", result );

 

[Randy Howard]

Hi there

I am planning to
open a lot of files name test1.txt, test2.txt ...
But I don't know how to change integer to be string
like 1 to char'1' and cantenate them with test and .txt

concatenate?


/* Make sure you have enough room in your result char array. */
char result[100];

Shouldn't this bear some resemblance to the maximum length of
a filename on the machine and any bizarre semantics about the
characters in the filename? (8.3 perhaps).

int filenumber = 10;

sprintf( result, "%s%d.txt", "filename", filenumber );

How do you check to make sure there is room? In a real implementation,
"filename" might be
"whatevertheuserhappenedtoenterwhenpromptedforafilenamejustbecauseicankeep
ontypinguntilIgetboredormypizzaisreadytotakeoutoftheoven"
depending on how the input is collected. That, plus some number, like
INT_MAX might make for a nice overflow with the above.

OTOH, if you know as the OP indicated that it will always be "test"%d,
you need only be sure that the strlen of "filenumber" (as a string) +
"test" + ".txt" + 1 isn't longer than result and that it does not violate
the filename conventions on the platform.

 

[Jeff]

Helen wrote:

[snip]

/* Make sure you have enough room in your result char array. */
char result[100];

Shouldn't this bear some resemblance to the maximum length of
a filename on the machine and any bizarre semantics about the
characters in the filename? (8.3 perhaps).

int filenumber = 10;

sprintf( result, "%s%d.txt", "filename", filenumber );

How do you check to make sure there is room? In a real implementation,
"filename" might be
"whatevertheuserhappenedtoenterwhenpromptedforafilenamejustbecauseicankeep
ontypinguntilIgetboredormypizzaisreadytotakeoutoftheoven"
depending on how the input is collected. That, plus some number, like
INT_MAX might make for a nice overflow with the above.

OTOH, if you know as the OP indicated that it will always be "test"%d,
you need only be sure that the strlen of "filenumber" (as a string) +
"test" + ".txt" + 1 isn't longer than result and that it does not violate
the filename conventions on the platform.


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SCO Spam-magnet: (e-mail address removed)

IMHO, the OP can decide that what size would be enough for the "char
result[]".

If buffer overflow is a problem, we can make use of malloc


#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void print_name(long filenumber)
{

char *result;
double var1;

var1 = log10(filenumber);

result = malloc((long)var1 + 4 + 1);
/* adding 1 for rounding double to long, adding 4 for ".txt", adding 1 for
terminating null character */

sprintf( result, "%s%d.txt", "file", filenumber );
puts(result);

free(result);

}

int main()
{
print_name(99999999);

return 0;
}

 

[Irrwahn Grausewitz]

/* Make sure you have enough room in your result char array. */
char result[100];

int filenumber = 10;

sprintf( result, "%s%d.txt", "filename", filenumber );

How do you check to make sure there is room? In a real implementation,
"filename" might be
"whatevertheuserhappenedtoenterwhenpromptedforafilenamejustbecauseicankeep
ontypinguntilIgetboredormypizzaisreadytotakeoutoftheoven"
depending on how the input is collected. That, plus some number, like
INT_MAX might make for a nice overflow with the above.

In C99 one could use snprintf and dynamically allocate the buffer to
make sure there's enough space to hold the resulting string.

 

[Martin Dickopp]

/* Make sure you have enough room in your result char array. */
char result[100];

Shouldn't this bear some resemblance to the maximum length of
a filename on the machine

That would make it harder to port to systems which don't have a fixed
limit on the filename length. IMHO, it's usually better to code under the
assumption that *nothing* is arbitrarily limited whenever possible.

Martin

 

[Tom Zych]

How do you check to make sure there is room? In a real implementation,
"filename" might be
"whatevertheuserhappenedtoenterwhenpromptedforafilenamejustbecauseicankeep
ontypinguntilIgetboredormypizzaisreadytotakeoutoftheoven"
depending on how the input is collected. That, plus some number, like
INT_MAX might make for a nice overflow with the above.

As posted[1], "filename" can only be "filename"

[1] Which is probably not what Aggro meant to type.

 

[Randy Howard]

That would make it harder to port to systems which don't have a fixed
limit on the filename length. IMHO, it's usually better to code under the
assumption that *nothing* is arbitrarily limited whenever possible.

I agree, provided that it doesn't actually have to work on one of
the aforementioned systems.

 

[Randy Howard]

How do you check to make sure there is room? In a real implementation,

As posted[1], "filename" can only be "filename"
[1] Which is probably not what Aggro meant to type.

Which is precisely why I said "real implementation" above.

 

[Charles Richmond]

Hi there

I am planning to
open a lot of files name test1.txt, test2.txt ...
But I don't know how to change integer to be string
like 1 to char'1' and cantenate them with test and .txt

You can "catentate" the strings...and you can "concatenate"
the strings. But there is *no* such thing as "cancatenate".

 

[pete]

You can "catentate" the strings...and you can "concatenate"
the strings. But there is *no* such thing as "cancatenate".

Worst spelling flame ever!

 

[Joona I Palaste]

You can "catentate" the strings...and you can "concatenate"
the strings. But there is *no* such thing as "cancatenate".

So? Please show me where Helen used the word "cancatenate".

--
/-- Joona Palaste ([email protected]) ---------------------------\
| Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++|
| http://www.helsinki.fi/~palaste W++ B OP+ |
\----------------------------------------- Finland rules! ------------/
"I am not very happy acting pleased whenever prominent scientists overmagnify
intellectual enlightenment."
- Anon

 

[Joe Wright]

You can "catentate" the strings...and you can "concatenate"
the strings. But there is *no* such thing as "cancatenate".

She said "cantenate", and it's not nice to correct spilling errors.