vim, 25 bytes

Result

AC

Duration

871ms

Code [DL]

:%s/\v.+(.)(\1| ).+/\1
ZZ

Disassembly

:%s/\v.+(.)(\1| ).+/\1<NL>ZZ

stdin

825 238
734 341
711 723
974 474
788 912
128 917
722 255
766 967
723 824
794 945
891 991
564 463
453 336
518 831
873 994
633 634
248 227
346 845
267 626
477 991
191 123
523 837
773 779
577 793
533 331
339 949
651 917
564 931
285 552
811 471
722 118
399 997

stdout

5
4
1
4
8
8
2
6
3
4
9
4
3
8
9
3
2
6
7
9
1
3
7
7
3
9
1
4
5
1
1
9

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffed6b61d50 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x55bc79ad7d00 /* 9 vars */) = 0
11    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
12    execve("/usr/bin/vim", ["/usr/bin/vim", "-N", "-u", "NONE", "-i", "NONE", "-s", "/volume/CODE", "/tmp/out"], 0x55bc7b9e1288 /* 10 vars */) = 0
12    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    execve("/bin/cat", ["cat", "/tmp/out"], 0x55bc79ad7c98 /* 9 vars */) = 0
13    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
14    execve("/bin/rm", ["rm", "/tmp/out"], 0x55bc79ad7c98 /* 9 vars */) = 0
14    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=14, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
10    +++ exited with 0 +++