The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

  • My badges

  • Twitter Updates

  • My Flickr Stream

    20140508-Delphi-2007--Project-Options--Cannot-Edit-Application-Title-HelpFile-Icon-Theming20140430-Fiddler-Filter-Actions-Button-Run-Filterset-now20140424-VMware-Fusion-6.0.3.-no-reclaimable
    More Photos

  • Pages

  • All categories

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 1,840 other followers

Archive for the ‘bash’ Category

« Previous Entries

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
  1. pwd happens unconditionally
  2. (Grouping only)
  3. ls happens (in a subshell) unconditionally.
  4. cd .. happens if (3) failed.
  5. ls student/ happens if (3) failed and (4) succeeded
  6. (Grouping only)
  7. cd student happens if either (3) succeeded or both (4) and (5) succeeded.
  8. cd / happens if either [both (3) and one of (4) or (5) failed], or [(7) failed].
  9. cd happens 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

Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »

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 bash script 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:

Prefixes for multiples of
bits (bit) or bytes (B)
Decimal
Value SI
1000 k kilo
10002 M mega
10003 G giga
10004 T tera
10005 P peta
10006 E exa
10007 Z zetta
10008 Y yotta
Binary
Value IEC JEDEC
1024 Ki kibi K kilo
10242 Mi mebi M mega
10243 Gi gibi G giga
10244 Ti tebi –
10245 Pi pebi –
10246 Ei exbi –
10247 Zi zebi –
10248 Yi yobi –

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:

Read the rest of this entry »

Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »

some links on bash and optional parameters

Posted by jpluimers on 2019/11/26

Hopefully I’ve been able to integrate some of the ideas in the links below in github.com/jpluimers/btrfs-du/blob/master/btrfs-du

One of the features I wanted there was to be able to add optional switches like --raw, --iec or --si to it similar to what as the btrfs qgroup show subcommand has.

It seems possible with bash, but it is not trivial, at least not for me as a non-frequent bash user, so here are some links to get me started:

In retrospect, other languages than bash might have been a better choice for a script like that (:

–jeroen

PS, some btrfs references:

Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »

How to Update All Your Ruby Gems At Once | Life, the Universe, and Everything

Posted by jpluimers on 2019/08/26

This looks smart

gem update `gem list | cut -d ' ' -f 1`

From: [WayBack] How to Update All Your Ruby Gems At Once | Life, the Universe, and Everything

Though on the bash prompt, it works fine on Mac OS X / OS X / macOS / …, it does not work nice as an alias.

You can get it to work with difficult escaping (or nesting).

But it is easier to escape this:

gem update $(gem list | cut -d ' ' -f 1)

Escaped, it comes down to:

alias "gem-update-all=gem update \$(gem list | cut -d ' ' -f 1)"

Based on:

–jeroen

Posted in Apple, bash, bash, Development, Mac OS X / OS X / MacOS, Power User, Scripting, Software Development | Leave a Comment »

Show SCSI / HBA modules in ESXi 6.5 with file and version information

Posted by jpluimers on 2019/05/02

A small script I made: Show SCSI / HBA modules in ESXi 6.5 with file and version information:

MODULES=`esxcfg-scsidevs --hbas | awk 'FNR > 0 {print $2}'`
for MODULE in $MODULES ; do
    # echo "Probing $MODULE"
    vmkload_mod --showinfo $MODULE | grep 'file: \|Version'
done

The script is based on ideas from [WayBack] Determining Network/Storage firmware and driver version in ESXi 4.x and later (1027206) | VMware KB

It works in at least ESXi 6.5 where it shows this on one of my systems:

 input file: /usr/lib/vmware/vmkmod/lsi_msgpt3
 Version: 12.00.02.00-11vmw.650.0.0.4564106
 input file: /usr/lib/vmware/vmkmod/vmw_ahci
 Version: 1.0.0-39vmw.650.1.26.5969303
 input file: /usr/lib/vmware/vmkmod/vmw_ahci
 Version: 1.0.0-39vmw.650.1.26.5969303
 input file: /usr/lib/vmware/vmkmod/vmw_ahci
 Version: 1.0.0-39vmw.650.1.26.5969303
 input file: /usr/lib/vmware/vmkmod/lsi_mr3
 Version: 6.910.18.00-1vmw.650.0.0.4564106
 input file: /usr/lib/vmware/vmkmod/megaraid_sas
 Version: Version 6.603.55.00.2vmw, Build: 4564106, Interface: 9.2 Built on: Oct 26 2016
 input file: /usr/lib/vmware/vmkmod/vmkusb
 Version: 0.1-1vmw.650.1.26.5969303

–jeroen

Read the rest of this entry »

Posted in bash, Development, ESXi6.5, Power User, Scripting, Software Development, Virtualization, VMware, VMware ESXi | Leave a Comment »

« Previous Entries
 
%d bloggers like this: