Commands by gpenguin

Commands by gpenguin (4)

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Insert a line at the top of a text file without sed or awk or bash loops

Just use '-' to use STDIN as an additional input to 'cat'
This is sample output - yours may be different.
3

echo "New first line" | cat - file.txt > newfile.txt; mv newfile.txt file.txt

gpenguin · 2018-10-18 18:54:24 0
View firewall config including devices on linux w/netfilter

I was previously unaware of the -v switch. As a result I never got specifics about which interfaces the allowed or dropped applied to. Thought I'd share the wealth... FYI, -n prevents DNS resolving of IPs.
This is sample output - yours may be different.
0

iptables -L -n -v

gpenguin · 2009-10-07 21:13:59 0
Generate SHA1 hash for each file in a list

All output is placed in file SHA1SUMS which you can later check with 'sha1sum --check'. Works on most Linux distros where 'sha1sum' is installed.
This is sample output - yours may be different.
2

find . -type f -exec sha1sum {} >> SHA1SUMS \;

gpenguin · 2009-10-05 18:33:59 2
Verify MD5SUMS but only print failures

All valid files are withheld so only failures show up. No output, all checks good.
This is sample output - yours may be different.
6

md5sum --check MD5SUMS | grep -v ": OK"

gpenguin · 2009-10-02 05:21:17 2

What's this?

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BASH one-liner to get the current week number

Not as cool as the python example, but it still works.

Right-align text in console using pipe like ( command | right )

Wordwrap long text string using "\n"

I used this fragment with Imagemagick convert so that I can place long text strings in pictures. The "\n" gets converted to a true newline in the image. So this fragment uses fold command to wrap the line and then sed to convert newlines (and any trailing spaces on the line) to the text "\n"

grep across a git repo and open matching files in gedit

Get information about memory modules

To take information about the characteristics of the installed memory modules.

Url Encode

trace the system calls made by a process (and its children)

strace can be invaluable in trying to figure out what the heck some misbehaving program is doing. There are number of useful flags to limit and control its output, and to attach to already running programs. (See also 'ltrace'.)

List the Sizes of Folders and Directories

I wanted an easy way to list out the sizes of directories and all of the contents of those directories recursively.

find sparse files

Prints the path/filename and sparseness of any sparse files (files that use less actual space than their total size because the filesystem treats large blocks of 00 bytes efficiently).

A simple command to toggle mute with pulseaudio (any sink)

0 can also be replaced by the source name, e.g. alsa_output.pci-0000_00_1b.0.analog-stereo

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