BEAUTY AND PLAY
$echo $BASH /bin/bash $echo $BASH_ $echo $BASH_v $echo $BASH_VERSION 4.3.42(1)-release $date || time Sun Feb 21 23:15:50 IST 2016 $datei || time bash: datei: command not found real 0m0.000s user 0m0.000s sys 0m0.000s $dateno || time bash: dateno: command not found real 0m0.000s user 0m0.000s sys 0m0.000s $time || date bash: syntax error near unexpected …
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$builtin echo jeffrin jeffrin $echo jeffrin jeffrin $echo() { echo “hi”; }; $echo jeffrin ^C $builtin echo jeffrin jeffrin $echo jeffrin ^C $ https://en.wikipedia.org/wiki/Shell_builtin http://unix.stackexchange.com/questions/11454/what-is-the- difference-between-a-builtin-command-and-one-that-is-not (jeffrin) what is the use of the command named “builtin” (jeffrin) llua : hello (llua) to avoid a possible wrapper
$tsort 1 tsort: -: input contains an odd number of tokens $tsort 1 2 1 2 $tsort 0 1 2 3 4 5 0 2 4 1 3 5 $tsort 0 1 2 3 4 5 0 2 4 1 3 5 $ http://www.geeksforgeeks.org/topological-sorting/ https://www.quora.com/What-are-some-real-world-applications-of-topological-sort
ABOUT strace strace is a diagnostic, debugging and instructional userspace utility for Linux. It is used to monitor and tamper with interactions between processes and the Linux kernel, which include system calls, signal deliveries, and changes of process state. The operation of strace is made possible by the kernel feature known as ptrace. TYPICAL strace …
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ABOUT env env is a shell command for Unix and Unix-like operating systems. It is used to either print a list of environment variables or run another utility in an altered environment without having to modify the currently existing environment. Using env, variables may be added or removed, and existing variables may be changed by …
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$mkdir data $cd data/ $ls $pwd /home/jeffrin/data $echo hello > file1.txt $echo world > file2.txt $ls -l total 8 -rw-r–r– 1 jeffrin jeffrin 6 Jan 22 22:44 file1.txt -rw-r–r– 1 jeffrin jeffrin 6 Jan 22 22:44 file2.txt $getfacl -R . > permissions.txt $cat permissions.txt # file: . # owner: jeffrin # group: jeffrin user::rwx group::r-x …
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$cat name.txt 1 ram 2 shyam 3 raju 4 biju $cat company.txt 1 google 2 facebook 3 twitter 4 ibm $join company.txt name.txt 1 google ram 2 facebook shyam 3 twitter raju 4 ibm biju $join name.txt company.txt 1 ram google 2 shyam facebook 3 raju twitter 4 biju ibm $
$ss -t State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 0 192.168.0.100:57982 216.58.197.34:https ESTAB 0 0 192.168.0.100:56572 216.58.196.98:https ESTAB 0 0 192.168.0.100:51440 216.58.220.34:https ESTAB 0 0 192.168.0.100:56850 216.58.196.110:https ESTAB 0 0 192.168.0.100:42946 216.58.220.46:https ESTAB 0 0 192.168.0.100:42758 216.58.197.46:https ESTAB 0 0 192.168.0.100:32912 216.58.220.33:https ESTAB 0 0 192.168.0.100:40452 216.58.220.38:https ESTAB 0 0 192.168.0.100:51128 182.79.251.80:https ESTAB …
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ABOUT TCP FLAGS They are control bits that indicate different connection states or information about how a packet should be handled. FLAGS CWR – Congestion Window Reduced (CWR) flag is set by the sending host to indicate that it received a TCP segment with the ECE flag set (added to header by RFC 3168). ECE …
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$sudo strace -e trace=signal -p 1 [sudo] password for jeffrin: Process 1 attached kill(4659, SIGTERM) = 0 kill(4659, SIGCONT) = 0 $gcc crtlc1-p1.c $./a.out Hello world Hello world Hello world Hello world Hello world Hello world Hello world Hello world Hello world ^Ci got a signal 2 Hello world Hello world ^C $cat crtlc1-p1.c #include …