Linux Format - UK (2019-12)

12 LXF257 December 2019 http://www.linuxformat.com

ANSWERS

This will remove most, but not all, ANSI

codes. Fortunately, the ones it misses are

all covered by col. This program is part of

the util-linux package so it will already be

installed by your distro. As it also reads

from stdin and writes to stdout, you can

combine the two commands in one pass:

$ ansi2txt <typescript | col -b

>typescript.txt

This should work for you, but bear in

mind the warning from the ansi2txt man

page: “All ANSI codes are simply ignored,

including all cursor positioning ones.

Sometimes this is what you want,

sometimes it isn’t.”

Q

Pi in the middle

I recently acquired a Raspberry Pi

3 B+ (yes, I’m late to the Pi party!).

I have a use case in mind for it that

I’d like some guidance with.

We are going travelling in a few

months and I’m looking for a way of

using the Pi as a headless and input-

device-less conduit to upload batches of

photos to the cloud whenever we stay in

a hostel with wireless internet. Physically

getting the SD card from the camera

connected to the Pi is trivial – I have a

small USB card reader for that. My

Q

Anti-ANSI help

You recommended the use of the

script command to record terminal

output. This has worked well for me,

thank you, but there is one gotcha. If any

program I run produces coloured output,

the typescript file that script produces

has ANSI codes splattered all over it. Is

there a way to have script record only

plain ASCII? Alternatively, is there a

relatively easy way to remove these

codes from the file?

Suzette Blanchard

A

You cannot tell script to not record

those codes as it is designed to

produce a faithful record of the terminal

session that can be viewed with script

replay. For a quick way to view a clean

version of the file, the less pager removes

the majority of such codes. If you want to

remove them from the file permanently,

you can use the ansi2txt command.

This is not installed by default on most

distros but you will get it by installing the

colorized-logs package – their spelling,

not mine! It reads from standard input and

sends the cleaned-up version to standard

output, so run it like this:

$ ansi2txt <typescript >typescript.txt

Got a burning question about open source or the kernel?

Whatever your level, email it to [email protected]

stumbling block is that I think I’ll need

the wireless network on the Pi for two

distinct uses: to connect to a hostel’s

wireless and thus the internet, and to

pair with my phone so I can ssh in order

to run a script to upload the photos from

the SD card.

I don’t think I can have both wireless

modes ‘active’ at the same time. My

question probably boils down to, how

might I be able to connect the Pi to a

hostel’s wireless without having a

keyboard and display attached in order

to enter a wireless password? I think I

might have to set up the Pi as an access

point that I can connect my phone to,

download photos from the SD card onto

my phone, and then switch my phone to

connect to a hostel’s wireless in order to

do the upload as a separate step. But

this setup would likely restrict what else

I could use the Pi for, as it wouldn’t be

connected to the internet itself.

Matthew Wise

A

What you want to do should be

possible, but not that simple. The

first problem is connecting to the wireless

without a display and keyboard. With a

standard wireless setup, you can usually

edit the wpa_supplicant configuration file

to add an access point and password, but

many places do not use such a simple

setup. Many use a landing page where you

are required to use a web browser to login

before you can access the internet, which

is rather difficult without a display.

There is a way round this: add a second

wireless interface to the Pi on a USB

dongle. Then you can set up one interface

as an access point and connect to it from

your phone. Once the two are connected,

you can then use VNC to put the Pi’s

display on the phone and then set up the

wireless internet connection and copy your

files to the cloud.

You could possibly skip the second

wireless interface if your phone supports

USB networking: you could use a USB

cable for that connection and the Pi’s

onboard wireless to connect to the net.

If you really want to involve your Raspberry Pi in your travels, set it up at home as a repository for your photos.

A recent Pi is more than capable of running a single-user cloud.

Answers

Neil

Bothwick

uses old

Windows

DVDs to

carve Tux-

shaped toys.

12 LXF257 December 2019 http://www.linuxformat.com

Thiswillremovemost,butnotall,ANSI

codes.Fortunately,theonesit missesare

allcoveredbycol. Thisprogramispartof

theutil-linuxpackagesoit willalreadybe

installedbyyourdistro.Asit alsoreads

fromstdinandwritestostdout,youcan

combinethetwocommandsinonepass:

$ ansi2txt<typescript| col-b

>typescript.txt

Thisshouldworkforyou,butbearin

mindthewarningfromtheansi2txtman

page:“AllANSIcodesaresimplyignored,

includingallcursorpositioningones.

Sometimesthisiswhatyouwant,

sometimesit isn’t.”

Q

Piinthemiddle

I recentlyacquireda RaspberryPi

3 B+(yes,I’mlatetothePiparty!).

I havea usecaseinmindforit that

I’dlikesomeguidancewith.

Wearegoingtravellingina few

monthsandI’mlookingfora wayof

usingthePiasa headlessandinput-

device-lessconduittouploadbatchesof

photostothecloudwheneverwestayin

a hostelwithwirelessinternet.Physically

gettingtheSDcardfromthecamera

connectedtothePiistrivial– I havea

smallUSBcardreaderforthat.My

Q

Anti-ANSIhelp

Yourecommendedtheuseofthe

scriptcommandtorecordterminal

output.Thishasworkedwellforme,

thankyou,butthereisonegotcha.If any

programI runproducescolouredoutput,

thetypescriptfilethatscriptproduces

hasANSIcodessplatteredalloverit.Is

therea waytohavescriptrecordonly

plainASCII?Alternatively,istherea

relativelyeasywaytoremovethese

codesfromthefile?

SuzetteBlanchard

A

You cannot tell script to not record

those codes as it is designed to

produce a faithful record of the terminal

session that can be viewed with script

replay. For a quick way to view a clean

version of the file, the less pager removes

the majority of such codes. If you want to

remove them from the file permanently,

you can use the ansi2txt command.

Thisisnotinstalledbydefaultonmost

distrosbutyouwillgetit byinstallingthe

colorized-logspackage– theirspelling,

notmine!It readsfromstandardinputand

sendsthecleaned-upversiontostandard

output,sorunit likethis:

$ ansi2txt<typescript>typescript.txt

Gota burningquestionaboutopensourceorthekernel?

Whateveryourlevel,emailit [email protected]

stumbling block is that I think I’ll need

the wireless network on the Pi for two

distinct uses: to connect to a hostel’s

wireless and thus the internet, and to

pair with my phone so I can ssh in order

to run a script to upload the photos from

the SD card.

I don’t think I can have both wireless

modes ‘active’ at the same time. My

question probably boils down to, how

might I be able to connect the Pi to a

hostel’s wireless without having a

keyboard and display attached in order

to enter a wireless password? I think I

might have to set up the Pi as an access

point that I can connect my phone to,

download photos from the SD card onto

my phone, and then switch my phone to

connect to a hostel’s wireless in order to

do the upload as a separate step. But

this setup would likely restrict what else

I could use the Pi for, as it wouldn’t be

connected to the internet itself.

MatthewWise

A

What you want to do should be

possible, but not that simple. The

first problem is connecting to the wireless

without a display and keyboard. With a

standard wireless setup, you can usually

edit the wpa_supplicant configuration file

to add an access point and password, but

many places do not use such a simple

setup. Many use a landing page where you

are required to use a web browser to login

before you can access the internet, which

is rather difficult without a display.

There is a way round this: add a second

wireless interface to the Pi on a USB

dongle. Then you can set up one interface

as an access point and connect to it from

your phone. Once the two are connected,

you can then use VNC to put the Pi’s

display on the phone and then set up the

wireless internet connection and copy your

files to the cloud.

You could possibly skip the second

wireless interface if your phone supports

USB networking: you could use a USB

cable for that connection and the Pi’s

onboard wireless to connect to the net.

If you really want to involve your Raspberry Pi in your travels, set it up at home as a repository for your photos.

A recent Pi is more than capable of running a single-user cloud.

Answers

Neil

Bothwick

uses old

Windows

DVDs to

carve Tux-

shaped toys.