c-gcc, 58 bytes

Result

AC

Code [DL]

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

stdin

3452815341561621308497271481424131864397388037205944021923024521029945979428377882724686406289210833

stdout

0000000011111111111222222222222222333333333334444444444444455555566666677777777888888888888999999999

stderr

/tmp/code.c:1:1: warning: data definition has no type or storage class
 s[1];main(){strcmp();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();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();qsort(gets(s),100,1,strcmp);puts(s);}
             ^
/tmp/code.c:1:13: warning: statement with no effect [-Wunused-value]
/tmp/code.c:1:22: warning: implicit declaration of function ‘qsort’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp();qsort(gets(s),100,1,strcmp);puts(s);}
                      ^
/tmp/code.c:1:28: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp();qsort(gets(s),100,1,strcmp);puts(s);}
                            ^
/tmp/code.c:1:50: warning: implicit declaration of function ‘puts’ [-Wimplicit-function-declaration]
 s[1];main(){strcmp();qsort(gets(s),100,1,strcmp);puts(s);}
                                                  ^
/tmp/cc6d96PF.o: In function `main':
code.c:(.text.startup+0xc): warning: the `gets' function is dangerous and should not be used.

strace