c-gcc, 61 bytes

Result

AC

Code [DL]

s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}

stdin

2907236116008090604291700270813355192154043973083494611485436512987117833916112953811528230103830004

stdout

0000000000000000111111111111111112222222223333333333333444444445555555666666777777888888888999999999

stderr

/tmp/code.c:1:1: warning: data definition has no type or storage class
 s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}
 ^
/tmp/code.c:1:1: warning: type defaults to ‘int’ in declaration of ‘s’ [-Wimplicit-int]
/tmp/code.c:1:6: warning: return type defaults to ‘int’ [-Wimplicit-int]
 s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}
      ^
/tmp/code.c: In function ‘main’:
/tmp/code.c:1:13: warning: implicit declaration of function ‘strcmp’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}
             ^
/tmp/code.c:1:25: warning: implicit declaration of function ‘qsort’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}
                         ^
/tmp/code.c:1:31: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}
                               ^
/tmp/code.c:1:53: warning: implicit declaration of function ‘puts’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp(s,s);qsort(gets(s),100,1,strcmp);puts(s);}
                                                     ^
/tmp/ccFpmzpj.o: In function `main':
code.c:(.text.startup+0xc): warning: the `gets' function is dangerous and should not be used.

strace