In this tutorial on Linux fold, 100 of 100, below find a 3-4 minute introductory video, a text-based tutorial and all of the code examples from the video.
Our one hundredth word, or command to memorize is
fold from our category
Text.
fold allows you to wrap text to a
specified width.
Common Linux fold Options
-options
description
--help
Print help screen
-b,
--bytes
Use bytes to limit width
-wN,
--width=N
Wrap at N number of columns, default is 80
Recall that since video (tutorial) #87, we've been using a script to
demonstrate workflow, and now we'll use
fold at the command line and then
see it in that script.
Before we start, it helps to think of commands as mini programs and
most follow this structure:
command -option(s) argument(s).
The fold command has
5 options and the argument is a file, or
alternatively fold will
work with standard input.
Like most commands, help is available with double-dash
--help, and
fold is specified with
-b for bytes, and
-w for words, to define the line on
where you will fold it.
So why is fold an important command?
Well, it'll help us wrap up the Playlist on an easy note.
;)
And now you know how to do that.
Demonstration
Okay, the best way to embed this in your memory is by typing in your
own terminal window.
Find this on your Mac using a program called Terminal. On Linux use
Terminal or Konsole, and currently Microsoft is adding this
functionality to Windows.
Here we go. Using echo let's create
"a long line of text that goes on and on and never seems to end."
$ echo "a long line of text that goes on and on and never seems to end"
a long line of text that goes on and on and never seems to end
Okay, there it is.
Now, to wrap this, we pipe it into
fold and use the option
-w15 to cut it right at the 15th
character.
$ echo "a long line of text that goes on and on and never seems to end" | fold -w15
a long line of
text that goes
on and on and n
ever seems to e
nd
Good, but notice how it cuts words here? So it isn't a perfect solution.
Next, let's see fold in action with our script that we started in video
(tutorial) #87. There is a lot to this, because we have building on it,
and I'll provide this code for you (below) if you'd like to
deconstruct it on your end.
$ funscript
This script does provide a good subset of what we've covered in
roughly 6 hours together.
The current date and time:
Wed Nov 23 00:43:58 PST 2016
What is your name? Paul
Thank you Paul
Lines and files since your last archive:
0 ./video79.script
5 ./video85a.txt
43 ./video91.txt
0 ./video75.txt
0 ./video76.txt
61 ./video85b.txt
109 total
You've been busy. See video91.txt for a list of files
Here are your last five files. Nice work!
video75.txt
video76.txt
video85a.txt
video85b.txt
video91.txt
We started with a print of recent work and a reminder to archive.
Right? If you recall from earlier scripting videos.
Please select from the following options:
(1) Show system status
(2) Collect returns data
(3) See a sample of the data
(4) Finish the Linux Essentials playlist
(5) Quit
Your choice: k
Next, we created a menu that catches errors. If you type something
that's not on that menu it will kick right back (hitting k triggered
it to loop back to the original menu.)
Please select from the following options:
(1) Show system status
(2) Collect returns data
(3) See a sample of the data
(4) Finish the Linux Essentials playlist
(5) Quit
Your choice: 1
You selected 1. One moment please...
Collecting system status
Disk space and % used
Size Use%
4.8G 1%
The first item will report the system status. And that runs through
and presents a disk status update for you.
Please select from the following options:
(1) Show system status
(2) Collect returns data
(3) See a sample of the data
(4) Finish the Linux Essentials playlist
(5) Quit
Your choice: 2
You selected 2. One moment please...
Collecting returns data
Investment modeling boot camp data downloaded
The second item will download a file from the extraordinarily useful
and helpful website factorpad.com ;)
and then third, we'll view the file.
Please select from the following options:
(1) Show system status
(2) Collect returns data
(3) See a sample of the data
(4) Finish the Linux Essentials playlist
(5) Quit
Your choice: 3
You selected 3. One moment please...
This is a sample of the data set
Date MSFT EBAY ABT MRK Market Tbill
4/30/2003 0.056175 0.089087 0.083536 0.062066 0.072716 0.001000
5/30/2003 -0.037544 0.094070 0.096480 -0.044689 0.027079 0.000900
6/30/2003 0.041853 0.023119 -0.017733 0.096319 0.035890 0.001000
7/31/2003 0.030031 0.031731 -0.100672 -0.087036 -0.031487 0.000700
8/29/2003 0.004165 0.032805 0.026752 -0.039496 0.006057 0.000700
9/30/2003 0.048265 -0.031944 0.055831 0.013306 0.021365 0.000800
10/31/2003 -0.054537 0.042692 0.004456 -0.125840 -0.033307 0.000700
11/28/2003 -0.016450 -0.000715 0.037072 -0.082486 -0.015645 0.000700
12/31/2003 0.064566 0.156021 0.054299 0.147581 0.105617 0.000800
This takes the top 10 lines and shows you what's in that file. We use
it for a boot camp video series.
And now we finish with fold.
Please select from the following options:
(1) Show system status
(2) Collect returns data
(3) See a sample of the data
(4) Finish the Linux Essentials playlist
(5) Quit
Your choice: 4
You selected 4.
Thank you for your time.
Let's finish up...
...by using the fold command on this line of text:
Very good (remember we will return to our final script in the next
tutorial).
I hear them out there Waves are folding, always do. Now we meet again
(Below is the fold.)
I hear them out there
Waves are folding, always do.
Now we meet again
A Final Tip
Okay now you know how to use fold.
And you know the syntax for commands, options and arguments.
One last tip about the fold command.
So for those who didn't fold, and made it through all 100 videos,
congratulations and thank you. I hope you learned a lot. And for the
first timers, this video provides a glimpse at our structure and an
outcome. So please join us.
Okay, thanks for visiting today. I hope this was a helpful
introduction to the fold command.
(Below is the code for this entire final project called
funscript.)
#!/bin/bash
# The shebang gives the absolute path to the executable program
# To see if it points to the right executable try: which bash
# This is our first script called funscript
# From video 95, we add four functions above other code
# First form uses: functions { commands return } syntax
# 1) Function prints system statistics
function fun_stats {
printf "\tCollecting system status\n"
echo "Disk space and % used"
df -h --output='size','pcent' /home
sleep 5s
return
}
# Second form uses: name () { command return } syntax
# 2) Function collects returns text file data from factorpad.com website
fun_returns () {
printf "\tCollecting returns data\n"
wget factorpad.com/returns.txt --quiet -O video95.txt
printf "\tInvestment modeling boot camp data downloaded\n"
sleep 5s
return
}
# 3) Function uses head to show the first 10 lines of that file
fun_summary () {
printf "\tThis is a sample of the data set\n"
head video95.txt
sleep 5s
return
}
# 4) Function completes the video Playlist with a fold command in video 100
fun_finish () {
printf "\n\t...by using the fold command on this line of text:\n"
sleep 3s
clear
echo -e " \n"
echo -e "I hear them out there Waves are folding, always do. Now we meet again\n"
sleep 6s
clear
echo -e " \n"
echo -e "I hear them out there Waves are folding, always do.Now we meet again\n" | fold -w29
sleep 10s
return
}
clear
# From video 87, print text and the current date/time
echo -e "\nThe current date and time:"
date
# From video 88, we measure the time to run the script
sleep 2s
# From video 89, we take input from the keyboard
echo -e "What is your name? \c"
read yourname
echo "Thank you $yourname"
# From video 90, report files and lines since last archive
echo "Lines and files since your last archive:"
find . -type f -cnewer "video73.tar" | xargs wc -l
# From video 91, use tee to print files and show last five
echo "You've been busy. See video91.txt for a list of files"
echo "Here are your latest five files. Nice work!"
ls *.txt | tee video91.txt | tail -5
# From video 92, use printf to start our next section
sleep 4s
clear
printf "Ok, %s, what would you like to do next?\n" $yourname
# From video 96, set up the while statement
while true; do
clear
# From video 94, use if to set up the menu
printf "\nPlease select from the following options:\n"
printf "\t(1) Show system status\n"
printf "\t(2) Collect returns data\n"
printf "\t(3) See a sample of the data\n"
printf "\t(4) Finish the Linux Essentials playlist\n"
printf "\t(5) Quit\n"
echo -e "\n Your choice: \c"
read -n 1 yourpick
if [[ "$yourpick" =~ [1-5] ]]; then
if [[ $yourpick == 1 ]]; then
printf "\n\tYou Selected 1. One moment please...\n"
sleep 2s
fun_status
continue
fi
if [[ $yourpick == 2 ]]; then
printf "\n\tYou selected 2. One moment please...\n"
sleep 2s
fun_returns
continue
fi
if [[ $yourpick == 3 ]]; then
printf "\n\tYou selected 3. One moment please... \n"
sleep 2s
fun_summary
continue
fi
if [[ $yourpick == 4 ]]; then
printf "\n\tYou selected 4.\n"
sleep 1s
printf "\n\tThank you for your time.\n"
sleep 1s
printf "\n\tLet's finish up...\n"
sleep 2s
fun_finish
break
fi
if [[ $yourpick == 5 ]]; then
printf "\n\tYou selected 5.\n"
sleep 1s
echo -e "\n\tThank you, have a nice day."
sleep 1s
break
fi
else
printf "\n\tInvalid input. Please try again\n"
sleep 2s
continue
fi
# From video 96, close out the while/do/done block
done
Learn More About The Series
For an overview of the 100 videos, the 8 quizzes, a cheat sheet, the
categories and a Q&A section, visit:
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announcements of new Linux content.
For the Outline to all 100 tutorials, click Outline
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