ruby, 47 bytes

Result

INVALID

Duration

867ms

Code [DL]

s=`dd`;1while s[/(T.{50}|K)\K /m]&&=$1[0];$><<s

stdin

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      K                                           

stdout

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      KKKKKKKKKKKKKKKKKKKKKKKKKKT                 

stderr

4+1 records in
4+1 records out

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffd740d01c0 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x5601d5648d40 /* 9 vars */ <unfinished ...>
12    execve("/usr/local/ruby-2.6.3/bin/ruby", ["/usr/local/ruby-2.6.3/bin/ruby", "/volume/CODE"], 0x5601d5648d60 /* 9 vars */ <unfinished ...>
11    <... execve resumed> )            = 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} ---
13    execve("/bin/dd", ["dd"], 0x561f5aa01860 /* 9 vars */) = 0
13    +++ exited with 0 +++
12    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=0, si_stime=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=7, si_stime=3} ---
10    +++ exited with 0 +++