Collection of cool things I learnt today.
Today I learned about git bisect. It performs a binary search between two git refs and execute a command on each version until it finds the commit where the result changes. (0 good, 1 bad, 125 skip). git bisect start # to enter bisect mode git bisect old(good) <ref> # specify old version git bisect new(bad) <ref> # specify new version git bisect run <command> # perform bisect using the command
Today I learned about the colon built-in : in bash. It has no effect beyond expanding its arguments. also it always returns 0 exit status. It can be useful as a replacement for echos for dynamic comments.
Today I learned that [ is actually a binary and a shell built-in. whereis [ # output => [: /usr/bin/[ which [ # output => [: shell built-in command
Today I learned about TTYs and PTYs and the command tty and stty. tty outputs the tty/pty the shell is running on. while stty sets tty/sty options and params. Those include AURT related configs, line discipline configs, and TTY driver’s configs. # display all configs stty -a The output will be something like the following: # tty general settings speed 38400 baud; rows 59; columns 224; line = 0; # special characters intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0; # switches (-) for off. -parenb -parodd -cmspar cs8 -hupcl -cstopb cread -clocal -crtscts -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8 opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0 isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc Here are examples of setting up some configs. ...
Today I learned about postmortem debugging in Python. 3 ways to add postmortem debugging into python worflow are: Running the python script using pdb directly. PDB will create a breakpoint when the problem will fail. python -m pdb script.py Using pdb postmortem inside an except statement. PDB will drop us a breakpoint in the line which raised the exception. try: something() except Exception: import pdb(); pdf.post_mortem() handle_exception() Using pdb postmortem with a test runner (Pytest). if the test fails, PDB will start. pytest test.py --pdb More
Today I learned about cloud management platforms. They complete IAC tools, and inventory tools. Incorporating monitoring and metering, orchestration and automation all in one tool. They are used to manage public and private clouds too. In contrast with solutions like apache cloudstack and openstack which manage hypervisors and cloud resources building a private cloud. CMPs come at a higher level and are used to manage clouds (openstack’s included). One of OSS options are Mist.io, Cloudify and ManageIQ.
Today I learned about chapters in mpv, how to use them and how useful they are especially with youtube and youtube-dl. The current chapter’s name is displayed among the video information (i shortcut). ! and @ moves to the previous and next chapter respectively.