Tag: bash

visual sleep in shell, and shell_utils repo information

I wrote previously about tmux_send_to_many and group_by shell tools that I authored.

Since then I got some more ideas for changes, and for new tool, so figured I'll make an honest git repo for it. Repo is on GitLab, and all the tools inside can be freely used.

While I was doing it, I fixed some things in tmux_send_to_many.

And then – I remembered that for long time I was missing “visual-sleep" type of tool. One that will show some progress information while it's working.

Enter vsleep.

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Automation for doing stuff in multiple windows in tmux

Tmux is terminal multiplexer. Kinda like old screen, but with much more functionality.

When I work on my servers, it's pretty common that I have to do the same things to multiple servers. To make my life easier I start tmux, and in there start many “windows", each related to work on single server.

I name the windows in a way that let's me quickly find them, without false positives.

For example, if I'd have to upgrade servers db1..db5 then I'd create windows “up-db1" .. “up-db5", and each window would work on single server.

This is already scriptable – let's assume I'd want to show uptime in all of the windows, I can:

tmux lsw -F '#W' | grep -E '^up-db[0-9]+$' | xargs -r -d$'\n' -I% tmux send-keys -t % uptime Enter

But this gets tedious fast.

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Why does “sudo ls -l /proc/1/fd/*” fail?

I usually write about PostgreSQL, but lately someone asked for help, and one of the problems was similar to sudo command from title.

This was not the first time I saw it, so figured, I'll write a blogpost about it, just so I can refer people to it in the future.

Continue reading Why does “sudo ls -l /proc/1/fd/*" fail?

A tale of automating tests of Pg with Bash

Word of warning: this blogpost is about thing related to Bash (well, maybe other shells too, didn't really test), but since I found it while doing Pg work, and it might bite someone else doing Pg related work, I decided to add it to “postgresql" tag.

So, due to some work I had to do, I needed a quick, repeatable way to setup some Pg instances, replication between them, and some data loader. All very simple, no real problems. At least that's what I thought…

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Parallel dumping of databases

Some time ago I wrote a piece on speeding up dump/restore process using custom solution that was parallelizing process.

Later on I wrote some tools (“fast dump and restore") to do it in more general way.

But all of them had a problem – to get consistent dump you need to stop all concurrent access to your database. Why, and how to get rid of this limitation?

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Reduce bloat of table without long/exclusive locks

Some time ago Joshua Tolley described how to reduce bloat from tables without locking (well, some locks are there, but very short, and not really intrusive).

Side note: Joshua: big thanks, great idea.

Based on his idea and some our research, i wrote a tool which does just this – reduces bloat in table.

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Tips N’ Tricks – using GNU Screen as shell

I'm quite often doing stuff on remote machines, and quite frequently I start some long-running job, when I remember that I didn't ran it via screen – so it will break, if my network connection will die.

Is there any sane way to start screen automatically? YES.

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Set operations in shell

I had this interesting case at work. We have imports of objects. Each object in import file has its “ID" (which can be any string). Same “ID" is in database.

So the idea is pretty simple – we can/should check how many of IDs from import were in database. Unfortunately – we'd rather not really do the comparison in DB, as it is pretty loaded.

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