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Linux utils that you might not know

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Re: Linux utils that you might not know

#91

Post by squarefoot »

Mgen and Drec. No idea if they have been included in any modern distro, or there are more modern equivalents, anyway over 15 years ago I used them on Alpha hardware under both Linux, BSD and Tru64 to test a local network for missing UDP packets now and then in a strange regular pattern. By missing packets now and then I mean figures like 5 packets every 3 millions at full speed, it wasn't something one could hope to reproduce just by pinging around, therefore we needed something to leave during night hours running and writing huge logs. Turned out that it was an interrupt triggered by the video subsystem on the Alpha machines only under Tru64 that grabbed 100% of the CPU for a very short time, but enough to make the receiving task miss a few packets. Once identified the problem I was able to reproduce and predict it with 100% accuracy.

https://www.nrl.navy.mil/itd/ncs/products/mgen

ps. ...I know, I know, but sadly no way to make them change the protocol used.

Re: Linux utils that you might not know

#92

Post by cyphar »

effie wrote: post #81
sigi45 wrote: post #55

Show sorted list with human readable file/foldersize: du -hs * | sort -h

Tha shows only some files. To list all files, use: du -hs * .* | sort -h

Or if you (like me) hate depending on globbing semantics:

$ find . -mindepth 1 -maxdepth 2 -print0 | xargs -0 -- du -hs

Not that I would write it in a shell. ;)

Re: Linux utils that you might not know

#93

Post by cyphar »

sabujp wrote: post #34
sabujp wrote: post #29

factor is buggy : factor 100000000000000000000000000000000000000 100000000000000000000000000000000000000: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 http://www.wolframalpha.com/input/?i=factor+1000000000000000... also numfmt bug: $ numfmt --to=iec 999999999999999999939999999 828Y $ numfmt --to=iec 999999999999…

hrrm but bc -l shows : 999999999999999999939999999 / 1024^8 827.18061255302767482177

The output of the error is not using IEC units -- YB not YiB (IEC units have a lowercase "i" when written). So it's referring to yottabytes not yobibytes.

Re: Linux utils that you might not know

#94

Post by dom0 »

angry_octet wrote: post #83
dom0 wrote: post #61

Earlier quoted context omitted.

In data=journal mode, data to be written is first written into the journal. Only after the journal is flushed it will be written out to the correct location. Therefore, a crash at any time is fixed by replaying the journal forwards. Note that the ext3/4 journal is a redo log, not an undo log. Old file contents are not copied into the journal on a write. Thus, I don't see why shred should be less effective in data=jou…

There is no reason for blocks that have been fully rewritten to be written back to the same location. In fact, it is faster to write them somewhere convenient near the write head and update the indirect block. So even though only the meta data goes through the log, block locations can change.

As I suggested above that's an option independent of the journaling mode.

Re: Linux utils that you might not know

#95

Post by vog »

angry_octet wrote: post #90
vog wrote: post #76

Earlier quoted context omitted.

Although these tools are great, I'm afraid these are of limited use, as these aren't preinstalled but must be explicitly installed. For personal use these are great. But if you write a shell script to be executed on different machines where you can't install anything, these tools won't be available to you. And if you don't have that requirement, i.e. you can install everything, just install appropriate Perl/Python/Ru…

Why assume python? It's huge compared to bash or perl. Lots of minimal configuration operational systems won't have python. More likely than go/ruby/node though.

I had the impression that more an more system/initialization scripts are written in Python, at places where shell and perl were used in the past.

And having a system using Python on startup is a pretty good indicator that Python will be preinstalled.

However, I see that the situation may be different in specialized distros.

Re: Linux utils that you might not know

#96

Post by eeZah7Ux »

noja wrote: post #36
ivanstojic wrote: post #15

It always pains me when I see people use "cat" left and right, even when they don't need it. This makes for good reading: http://porkmail.org/era/unix/award.html

It shouldn't. It's 2017 now, and the speed difference between a "misplaced" cat command is normally negligible. The speed of the terminal user is more important.

Also, it makes it easier to add new commands that are not able to read from file in the existing pipeline.

Re: Linux utils that you might not know

#97

Post by discreditable »

Aissen wrote: post #68

Just look at anything in the "moreutils" package. Just great stuff. Excerpt: - ifdata: do not parse the output of ifconfig/ip anymore. Just use this tool. - sponge: when you need to overwrite an input file at the end of pipe. sponge will wait for the pipe to end before overwriting, preventing any data loss - vidir: edit a given dir with your EDITOR. Awesome for mass renames/deletes. - ts: add timestamps to a command…

One of my favorite moreutils tools is combine[1]. It allows you to compare the contents of text files with boolean operations. For example, want to know what lines are in file1 but not file2? Use:

    combine file1 not file2
1. http://manpages.ubuntu.com/manpages/zesty/en/man1/combine.1....

Re: Linux utils that you might not know

#100

Post by dabber »

brettproctor wrote: post #20

Anyone here will probably enjoy checking out commandlinefu: http://commandlinefu.com Especially looking down the list of all time greats: http://www.commandlinefu.com/commands/browse/sort-by-votes

Thanks for the second link. I go there every few weeks but never thought to check out the top voted.

...In hindsight, of course...

The gem I just plucked out is something I've been curious about for a while but never looked up:

    CTRL-X e
    
    The shell will take what you've written on the command 
    line thus far and paste it into the editor specified by 
    $EDITOR [then run it when saved]
Similar to `fc` except you don't need to run the command before invoking the editor
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