How to left pad a string with spaces?

[nospam]

If I have a string say:

myvar[128] = "This is a string";

How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:

" This is a string";
Thanks!

[Ben Bacarisse]

Richard<rg****@ gmail.comwrites :

Ben Bacarisse <be********@bsb .me.ukwrites:

<snip>

>void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}

I would also point out to the beginner, and "Chuck", to read the man
pages and to see why memmove is better than memcpy in this and other
situations.

That is an odd way of putting it. memmove is *essential* in this
situation. In other situations memcpy may be better. I did not
explain because someone else has already done so.

--
Ben.

[Richard]

Ben Bacarisse <be********@bsb .me.ukwrites:

Richard<rg****@ gmail.comwrites :

>Ben Bacarisse <be********@bsb .me.ukwrites:

<snip>

>>void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}

I would also point out to the beginner, and "Chuck", to read the man
pages and to see why memmove is better than memcpy in this and other
situations.

That is an odd way of putting it. memmove is *essential* in this
situation. In other situations memcpy may be better. I did not
explain because someone else has already done so.

I didnt see any other post on the matter. "better" is mentioned to get
people to read the man pages. Self help and all that. I see nothing odd
at all in mentioning it as "better".

[Ben Bacarisse]

Richard<rg****@ gmail.comwrites :

Ben Bacarisse <be********@bsb .me.ukwrites:

>Richard<rg**** @gmail.comwrite s:

>>Ben Bacarisse <be********@bsb .me.ukwrites:

<snip>

>>>void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}
I would also point out to the beginner, and "Chuck", to read the man
pages and to see why memmove is better than memcpy in this and other
situations.

That is an odd way of putting it. memmove is *essential* in this
situation. In other situations memcpy may be better. I did not
explain because someone else has already done so.

I didnt see any other post on the matter.

Message ID: <6b************ *@mid.uni-berlin.de Jens Thoms Toerring:

"Note the use of memmove() instead of memcpy() which is required
since source and destination overlap."

--
Ben.

[pete]

nospam wrote:

If I have a string say:

myvar[128] = "This is a string";

How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:

" This is a string";

/* BEGIN new.c */

#include <stdio.h>

int main(void)
{
char myvar[128] = "This is a string";

sprintf(myvar, "%20s", "This is a string");
puts(myvar);
return 0;
}

/* END new.c */

--
pete

[CBFalconer]

Ben Bacarisse wrote:

CBFalconer <cb********@yah oo.comwrites:

.... snip ...

>

> void sstretch(char *s, int amount) {
char *p1, *p2;

if (amount) {
pi = strchr(s, '\0');
if ((p1 s) && amount) {
p2 = p1 + amount;
do { /* move the string */
*p2-- = *p1--;
} while {p1 s);
}
while (amount) { /* inject the blanks */
*s++ = ' ';
amount--;
}
}
} /* untested */

Yuck. Two typos and two logic errors. You complain about not posting
corrections, so the correction is:

void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}

One does it for the exercise. I see only one typo [while {p1 >
s)]] and one unnecessary test [&& amount]. A compilation may well
show up more. What did you see?

Incidentally, a speed comparison would be interesting. I don't
think your version allows for amount == 0 and for an empty original
string. I would have to check the specs for memove and memset with
care.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.
** Posted from http://www.teranews.com **

[CBFalconer]

Ben Bacarisse wrote:

Richard<rg****@ gmail.comwrites :

>Ben Bacarisse <be********@bsb .me.ukwrites:

<snip>

>>void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}

I would also point out to the beginner, and "Chuck", to read the
man pages and to see why memmove is better than memcpy in this
and other situations.

That is an odd way of putting it. memmove is *essential* in this
situation. In other situations memcpy may be better. I did not
explain because someone else has already done so.

Richard is a troll. I didn't use memmove, but did the move coding
directly.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.

** Posted from http://www.teranews.com **

[Richard Heathfield]

Ben Bacarisse said:

Richard<rg****@ gmail.comwrites :

>Ben Bacarisse <be********@bsb .me.ukwrites:

<snip>

>>void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}

I would also point out to the beginner, and "Chuck", to read the man
pages and to see why memmove is better than memcpy in this and other
situations.

That is an odd way of putting it. memmove is *essential* in this
situation.

Um, no, it isn't. You /can/ bully the bytes around by hand if you prefer
(but if you do so, you need to push them *just so*, or they'll turn on
you). If you just meant that memcpy is a non-starter here, then of course
I agree.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[rio]

"nospam" <[e-mail] a scritto nel messaggio
news:co******** *************** *******@comcast .com...

If I have a string say:

myvar[128] = "This is a string";

How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:

>
" This is a string";
Thanks!

it not use sprint not tested

/* return the string if ok
0 if error
using like:
char *pc;
char *s="This is a string"

if((pc=the4spac es(s))==0) Error();
use(pc);
....
free(pc);
*/
char* the4spaces(char * s)
{char *p1, *p2, p;
unsigned c, sz;
/*************** *****/
if(s==0) return 0;
if( (int) (sz=strlen(s)) < 0) return 0;
p=p2=malloc(sz+ 8);
if(p2==0) return 0;
p1=s;
while( *p1 && (*p1==' '||*p1=='\t')) ++p1;
*p2++=' '; *p2++=' '; *p2++=' '; *p2++=' ';
while(*p2++=*p1 ++);
return p;
}

[rio]

"rio" <[e-mail] scritto nel messaggio
news:48******** *************** @reader5.news.t in.it...

>
"rio" <[e-mail] scritto nel messaggio news:484e3100$0 $18150/*

> one better version?
d should be mallocched or 0
e.g.
char *d=0;
unsigned sz=0;
----
if((sz=the4spac es(&d, sz, string))==0) error();
free(*d);
----------
*/

unsigned the4spaces(char ** d, unsigned sz, char* s)
{char *p1, *p2, p;
unsigned c, sz, r;
/*************** *****/
if(s==0) goto l0;
if( (int) (c=strlen(s)) < 0)
goto l0;
r=sz;

p=*d;

> if(c+4+1<sz)
{if( p=realloc(*d, c+8)==0)

arrrrrrrrrrrrrh hgjgjg ^^^^^^^^^^^^^^
if( (p=realloc(*d, c+8))==0)

> {l0:;
free(*d); *d=0; return 0;
}
r=c+8;

*d=p

> }
p1=s; p2=p; *d=p;

^^^^^^^not
p1=s; p2=p;

>while( *p1 && (*p1==' '||*p1=='\t')) ++p1;
*p2++=' '; *p2++=' '; *p2++=' '; *p2++=' ';
while(*p2++=*p 1++);
return r;
}

this seems good
not know if compile

[rio]

"CBFalconer " <cb********@yah oo.comha scritto nel messaggio
news:48******** *******@yahoo.c om...

Ben Bacarisse wrote:

>CBFalconer <cb********@yah oo.comwrites:

... snip ...

>>

>> void sstretch(char *s, int amount) {
char *p1, *p2;

if (amount) {
pi = strchr(s, '\0');
if ((p1 s) && amount) {
p2 = p1 + amount;
do { /* move the string */
*p2-- = *p1--;
} while {p1 s);
}
while (amount) { /* inject the blanks */
*s++ = ' ';
amount--;
}
}
} /* untested */

Yuck. Two typos and two logic errors. You complain about not posting
corrections, so the correction is:

void sstretch(char *s, size_t amount)
{
memmove(s + amount, s, strlen(s) + 1);
memset(s, ' ', amount);
}

One does it for the exercise. I see only one typo [while {p1 >
s)]] and one unnecessary test [&& amount]. A compilation may well
show up more. What did you see?

>> pi = strchr(s, '\0');

seems an error; should be p1= strchr(s, '\0');?

Incidentally, a speed comparison would be interesting. I don't
think your version allows for amount == 0 and for an empty original
string. I would have to check the specs for memove and memset with
care.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.
** Posted from http://www.teranews.com **