haskell, 77 bytes

Result

AC

Duration

1029ms

Code [DL]

main=interact$unlines.s((s(!).).zipWith max).lines
'K'!' '='K'
_!c=c
s=scanl1

stdin

                         T                        
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
           K                                      

stdout

                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
                         T                        
           KKKKKKKKKKKKKKT                        

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7fff8f4425a0 /* 7 vars */) = 0
12    execve("/usr/bin/runghc", ["/usr/bin/runghc", "/volume/CODE"], 0x5556b9905d40 /* 7 vars */ <unfinished ...>
11    execve("/bin/cat", ["cat", "-"], 0x5556b9905d30 /* 7 vars */) = 0
12    <... execve resumed> )            = 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/lib/ghc-8.4.3/bin/runghc", ["/usr/lib/ghc-8.4.3/bin/runghc", "-f", "/usr/bin/ghc-8.4.3", "/volume/CODE"], 0x560a1c7d5168 /* 7 vars */) = 0
12    execve("/usr/bin/ghc-8.4.3", ["/usr/bin/ghc-8.4.3", "-ignore-dot-ghci", "-x", "hs", "-e", ":set prog \"/volume/CODE\"", "-e", ":main []", "/volume/CODE"], 0x7fff47db27a0 /* 7 vars */) = 0
12    execve("/usr/lib/ghc-8.4.3/bin/ghc", ["/usr/lib/ghc-8.4.3/bin/ghc", "-B/usr/lib/ghc-8.4.3", "-ignore-dot-ghci", "-x", "hs", "-e", ":set prog \"/volume/CODE\"", "-e", ":main []", "/volume/CODE"], 0x55a0d095d200 /* 7 vars */) = 0
17    execve("/bin/gcc", ["gcc", "-fno-stack-protector", "-DTABLES_NEXT_TO_CODE", "-B/usr/lib/ghc-8.4.3/integer-gmp"..., "--print-file-name", "libgmp.so"], 0x7ffe91a77e50 /* 7 vars */) = -1 ENOENT (No such file or directory)
17    execve("/usr/local/sbin/gcc", ["gcc", "-fno-stack-protector", "-DTABLES_NEXT_TO_CODE", "-B/usr/lib/ghc-8.4.3/integer-gmp"..., "--print-file-name", "libgmp.so"], 0x7ffe91a77e50 /* 7 vars */) = -1 ENOENT (No such file or directory)
17    execve("/usr/local/bin/gcc", ["gcc", "-fno-stack-protector", "-DTABLES_NEXT_TO_CODE", "-B/usr/lib/ghc-8.4.3/integer-gmp"..., "--print-file-name", "libgmp.so"], 0x7ffe91a77e50 /* 7 vars */) = -1 ENOENT (No such file or directory)
17    execve("/usr/sbin/gcc", ["gcc", "-fno-stack-protector", "-DTABLES_NEXT_TO_CODE", "-B/usr/lib/ghc-8.4.3/integer-gmp"..., "--print-file-name", "libgmp.so"], 0x7ffe91a77e50 /* 7 vars */) = -1 ENOENT (No such file or directory)
17    execve("/usr/bin/gcc", ["gcc", "-fno-stack-protector", "-DTABLES_NEXT_TO_CODE", "-B/usr/lib/ghc-8.4.3/integer-gmp"..., "--print-file-name", "libgmp.so"], 0x7ffe91a77e50 /* 7 vars */) = 0
17    +++ exited with 0 +++
12    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=17, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
14    +++ exited with 0 +++
16    +++ exited with 0 +++
18    +++ exited with 0 +++
15    +++ exited with 0 +++
13    +++ exited with 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=18, si_stime=7} ---
10    +++ exited with 0 +++