jeffrin – Page 32

a sample session with a “filter” named tr

$cat u.txt UPPERCASE $cat l.txt cat: l.txt: No such file or directory $tr A-Z a-z l.txt $cat u.txt UPPERCASE $cat l.txt uppercase $

sample session related to “command expansion” in Bash shell

$a=`time` real 0m0.000s user 0m0.000s sys 0m0.000s $a bash: a: command not found $a=`ls` $a bash: a: command not found $echo a a $echo $a a.txt b.txt trueangle $echo `a` bash: a: command not found $a=`ls` $b=time $echo $b time $b=`time` real 0m0.000s user 0m0.000s sys 0m0.000s $echo $b $b=`time` real 0m0.000s user 0m0.000s sys …

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using the dir() Built-in function in Python programming

>>> import struct >>> dir() # show the names in the module namespace [‘__builtins__’, ‘__doc__’, ‘__name__’, ‘struct’] >>> dir(struct) # show the names in the struct module [‘Struct’, ‘__builtins__’, ‘__doc__’, ‘__file__’, ‘__name__’, ‘__package__’, ‘_clearcache’, ‘calcsize’, ‘error’, ‘pack’, ‘pack_into’, ‘unpack’, ‘unpack_from’] >>> class Shape(object): def __dir__(self): return [‘area’, ‘perimeter’, ‘location’] >>> s = Shape() >>> dir(s) …

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sample session using “variable expansion” with Bash shell

$com=world $echo com com $echo $com world $x=hello $echo ${x}{com} hello{com} $echo ${x}${com} helloworld $echo $x$com helloworld $echo ${x}world helloworld $echo ${x} world hello world $echo $x world hello world $echo $xcom $echo $x com hello com $echo $x $com hello world $echo $x$com helloworld $echo $xcom $echo ${x}com hellocom $ $your_id=${USER}-on-${HOSTNAME} $echo “$your_id” jeffrin-on-debian …

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what is a nondeterministic algorithm ?

In computer science, a nondeterministic algorithm is an algorithm that, even for the same input, can exhibit different behaviors on different runs, as opposed to a deterministic algorithm. https://en.wikipedia.org/wiki/Nondeterministic_algorithm

sample session about “brace and tilde” expansions in Bash

$ls trueangle $echo hello > a.txt $echo killo > b.txt $cat {a,b}.txt hello killo $pwd /home/jeffrin/temp $cd ~ $pwd /home/jeffrin $cd tr trueangle/ trueangle.old/ $pwd /home/jeffrin $cd – /home/jeffrin/temp $pwd /home/jeffrin/temp $ls a.txt b.txt trueangle $

sample session about “alias expansion” in Bash

$ls -l 1 ls: cannot access ‘1’: No such file or directory $cat >> 1 hello $ls -l 1 -rw-r–r– 1 jeffrin jeffrin 6 Mar 20 23:38 1 $cat 1 hello $alias appendinput=”cat >>” $appendinput bash: syntax error near unexpected token `newline’ $appendinput app added $cat app added $

sample session with a bash shell expansion named “history expansion”

$! 1 bash: 1: command not found $!1 bash: !1: event not found $!+1 bash: !+1: event not found $!-1 ! 1 bash: 1: command not found $!! ! 1 bash: 1: command not found $!-0 bash: !-0: event not found $

getting choices listed directly with the first TAB

$p Display all 428 possibilities? (y or n) $p bash: p: command not found $cat .inputrc set show-all-if-ambiguous on $ related text: Specifies the duration Readline will wait for a character when reading an ambiguous key sequence (one that can form a complete key sequence using the input read so far, or can take additional …

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enclose one or more commands inside a pair of parentheses

$ls 1 $( ls date ) ls: cannot access date: No such file or directory $( `ls` date ) bash: 1: command not found $cat 1 B$ $( ls `date` ) ls: cannot access Mon: No such file or directory ls: cannot access Feb: No such file or directory ls: cannot access 22: No such …

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