trim 0s

[pemo]

Can anyone suggest a nice way to trim any leading zeros off of a string,
e.g., I'd like to take a string like 00000012 and convert it to 12.

Ta

pemo

 

[usr.root]

just use printf is ok

 

[pemo]

How so?

 

[S.Tobias]

Can anyone suggest a nice way to trim any leading zeros off of a string,
e.g., I'd like to take a string like 00000012 and convert it to 12.

strspn(..., "0") ?

 

[Zara]

Can anyone suggest a nice way to trim any leading zeros off of a string,
e.g., I'd like to take a string like 00000012 and convert it to 12.

Ta

pemo

char *s_ini="00000012";
char *s_final=s_ini;
while (*s_final=='0') s_final++;

 

[Christopher Benson-Manica]

strspn(..., "0") ?

size_t loc=strspn( mystring, "0" );
memmove( mystring, mystring+loc, strlen(mystring+loc)+1 );

 

[gladiator]

if string consists 0's in between the characters,
we can't use strspn.

right

 

[Christopher Benson-Manica]

if string consists 0's in between the characters,
we can't use strspn.

Sure you can. strspn() returns the number of characters spanned at
the beginning of the string it is passed that match the charset.
Characters matching charset at any other point in the string are
completely inconsequential.

 

[gladiator]

Thank you for clarification

 

[Kevin Handy]

Can anyone suggest a nice way to trim any leading zeros off of a string,
e.g., I'd like to take a string like 00000012 and convert it to 12.

Ta

pemo

sprintf(mystring, '%d", strtol(mystring, 0, 10))

....:==)

 

[Ben Hetland]

Can anyone suggest a nice way to trim any leading zeros off of a string,
e.g., I'd like to take a string like 00000012 and convert it to 12.

sprintf(s, "%ld", atol(s));

That assumes there are nothing more than the number itself in the
string, otherwise perhaps a loop with strtok to convert each "word" in
the string separately can to the trick. Simply convert every word that
starts with '0', and just strcpy the rest.


-+-Ben-+-

 

[Jack Klein]

sprintf(s, "%ld", atol(s));

....assuming you don't mind potential undefined behavior.

That assumes there are nothing more than the number itself in the
string, otherwise perhaps a loop with strtok to convert each "word" in
the string separately can to the trick. Simply convert every word that
starts with '0', and just strcpy the rest.

Never use (or recommend, especially in this group), the ato...
conversion functions. They are old dangerous hacks, and produce
undefined behavior if the result of the conversion is outside the
range of the destination type.

The original language standard introduced the strto... functions, also
prototyped in <stdlib.h>, that have fully defined behavior for any
input other than a null pointer. And they provide for error checking
as well.

 

[Ben Hetland]

Never use (or recommend, especially in this group), the ato...
conversion functions. They are old dangerous hacks, and produce
undefined behavior if the result of the conversion is outside the
range of the destination type.

Yes, thank you for pointing that out!
I stand corrected!

But error checking is not quite trivial with these functions either, and
I find perhaps something like the following function a bit more
convenient in many cases (for base 10 only):

bool str_to_long_checked( const char* s, long *n )
{
long v;
char *st = 0;
errno = 0;
v = strtol(s, &st, 10);
if (st == s || errno != 0 || (st && *st=='\0'))
return false;
*n = v;
return true;
}


BTW, what's the "new" strto... equivalent of the "old" atof function then?


-+-Ben-+-

 

[Mike Wahler]

BTW, what's the "new" strto... equivalent of the "old" atof function then?

strtod()

-Mike

 

[websnarf]

size_t loc=strspn( mystring, "0" );
memmove( mystring, mystring+loc, strlen(mystring+loc)+1 );

And what if the number is 0?

 

[websnarf]

char *s_ini="00000012";
char *s_final=s_ini;
while (*s_final=='0') s_final++;

Almost ... oh what the hell, might as well do it right:

for (i = 0; s_ini == '0'; i++) if (s_ini == '\0' && i > 0) {
i--;
break;
}

s_final = &s_ini;

Of course I am waiting for someone (you know who you are) to tell me
that "0" is an illegal string ...

 

[S.Tobias]

And what if the number is 0?

Who said anything about numbers? The OP only wanted to remove
all initial zeroes from a string.
http://dspace.dial.pipex.com/town/green/gfd34/art/bloopers.html
"This is a lovely picture ..." is very adequate here.

Seriously, I'm sure the OP has already discovered by now
what he really needed.

 

[Old Wolf]

char *s_ini="00000012";
char *s_final=s_ini;
while (*s_final=='0') s_final++;

Almost ... oh what the hell, might as well do it right:

for (i = 0; s_ini == '0'; i++) if (s_ini == '\0' && i > 0) {
i--;
break;
}

s_final = &s_ini;

Huh? Zara's version is far better than yours, by any yardstick.
You can't write stuff like this and then expect people to not
think you are a troll...

 

[websnarf]

pemo wrote:
Can anyone suggest a nice way to trim any leading zeros off of a
string, e.g., I'd like to take a string like 00000012 and convert
it to 12.

char *s_ini="00000012";
char *s_final=s_ini;
while (*s_final=='0') s_final++;

Almost ... oh what the hell, might as well do it right:

for (i = 0; s_ini == '0'; i++) if (s_ini == '\0' && i > 0) {
i--;
break;
}

s_final = &s_ini;

Huh? Zara's version is far better than yours, by any yardstick.

Really? I pick correctness as my yardstick. Try setting s_ini =
"0000"; and compare the two solutions.

You can't write stuff like this and then expect people to not
think you are a troll...

Oh yeah, I forgot "correctness" is off topic here in CLC. If the
solution doesn't obsess over some standards minutia it must be a troll.

 

[Old Wolf]

Zara wrote:
pemo wrote:
Can anyone suggest a nice way to trim any leading zeros off of a
string, e.g., I'd like to take a string like 00000012 and convert
it to 12.

char *s_ini="00000012";
char *s_final=s_ini;
while (*s_final=='0') s_final++;

Almost ... oh what the hell, might as well do it right:

for (i = 0; s_ini == '0'; i++) if (s_ini == '\0' && i > 0) {
i--;
break;
}

s_final = &s_ini;

Huh? Zara's version is far better than yours, by any yardstick.

Really? I pick correctness as my yardstick. Try setting s_ini =
"0000"; and compare the two solutions.

Both solutions give "" in that case. Zara's is easier to read by far.

Oh yeah, I forgot "correctness" is off topic here in CLC. If
the solution doesn't obsess over some standards minutia it
must be a troll.

Replacing a short one-liner with a 4 lines that do exactly the
same thing in a more inefficient and obfuscated way... troll.

I suspect you are going to say that you think "0000" with leading
zeroes removed is "0", and you also planned to write a program
that gives "0", but you accidentally wrote a program that gives "".

I think this just proves the point that the shorter, clearer
solution is less prone to errors (and that you should indent
your code properly).

But even then, you would have to say that "2222" with leading
2s removed is "2", and " \t" with leading whitespace removed
is "\t", which is something that I think most people would
disagree with. Unless you think '0' is some sort of special
character?