Almost 20 years old, but still a very nice read [Archive.is] David Korn Tells All – Slashdot.
Another funny story involving David Korn during the not-so open source times of Microsoft late last century: [WayBack] Korn Shell Story
–jeroen
Archive for the ‘bash’ Category
David Korn Tells All – Slashdot
Posted by jpluimers on 2020/05/21
Posted in *nix, *nix-tools, bash, bash, Development, History, Power User, Scripting, Software Development | Leave a Comment »
Bash Notes for Professionals book
Posted by jpluimers on 2020/05/12
For my reading list: Bash Notes for Professionals book
Download: [WayBack] BashNotesForProfessionals.pdf
Via: [WayBack] Bash Notes for Professionals – a book compiled from Stack Overflow Documentation released under Creative Commons BY-SA – ThisIsWhyICode – Google+
–jeroen
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bash – How to add a progress bar to a shell script? – Stack Overflow
Posted by jpluimers on 2020/03/17
From [WayBack] bash – How to add a progress bar to a shell script? – Stack Overflow (thanks Mitch Haile!):
You can implement this by overwriting a line. Use
\rto go back to the beginning of the line without writing\nto the terminal.Write
\nwhen you’re done to advance the line.Use
echo -neto:
- not print
\nand- to recognize escape sequences like
\r.Here’s a demo:
echo -ne '##### (33%)\r' sleep 1 echo -ne '############# (66%)\r' sleep 1 echo -ne '####################### (100%)\r' echo -ne '\n'
–jeroen
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linux – Bash: Command grouping (&&, ||, …) – Stack Overflow
Posted by jpluimers on 2020/02/18
Excellent answer at [WayBack] linux – Bash: Command grouping (&&, ||, …) – Stack Overflow by Charles Duffy:
Operator precedence for
&&and||is strictly left-to-right.Thus:
pwd; (ls) || { cd .. && ls student/; } && cd student || cd / && cd ;…is equivalent to…
pwd; { { { (ls) || { cd .. && ls student/; }; } && cd student; } || cd /; } && cd ; }…breaking that down graphically:
pwd; { # 1 { # 2 { (ls) || # 3 { cd .. && # 4 ls student/; # 5 }; # 6 } && cd student; # 7 } || cd /; # 8 } && cd ; # 9
pwdhappens unconditionally- (Grouping only)
lshappens (in a subshell) unconditionally.cd ..happens if (3) failed.ls student/happens if (3) failed and (4) succeeded- (Grouping only)
cd studenthappens if either (3) succeeded or both (4) and (5) succeeded.cd /happens if either [both (3) and one of (4) or (5) failed], or [(7) failed].cdhappens if (7) occurred and succeeded, or (7) occurred and succeeded.
Using explicit grouping operators is wise to avoid confusing yourself. Avoiding writing code as hard to read as this is even wiser.
–jeroen
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bash: converting numbers to human readable SI or IEC units
Posted by jpluimers on 2019/12/03
Many unix tools that report sizes in bytes can convert them to either IEC or SI readable formats.
For github.com/jpluimers/btrfs-du/blob/master/btrfs-du I wrote about last week, I also wanted that kind of behaviour. So I did some research and came up with the code and test cases below.
Note that depending on the bitness of your system, bash integer numeric values are limited in size; see [WayBack] What is the maximum value of a numeric bash shell variable? – Super User.
So I wrote a small
bashscript for that too, which needed also gave me the opportunity to show how a perpetual while loop as explained by [WayBack] bash – “while :” vs. “while true” – Stack Overflow.Two things that always bite me with these short scripts are expressions (done through [WayBack]Arithmetic Expansion) and comparisons (through[WayBack] Other Comparison Operators).
The IEC suffixes contain one extra i to indicate binary and – next to the ISO notation that were already ISO defined – made it into the ISO 80000 standard since 2008. Here is a comparison list from [WayBack] Binary prefix – Wikipedia:
Most tools nowadays default to binary IEC suffixes for byte sizes, though disk manufacturers still use SI suffixes because, well then they appear bigger but aren’t. Just for comparison, look at the numbers from [WayBack] File size – Wikipedia and [WayBack] IEC and SI Size Notations – AN!Wiki where I got the test cases from:
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