Write text to Shell Script

Question

I am making a Shell Script, and I have to record a lot of lines in a single file, how can I do this more automatically? 'Cause I started doing it in a very manual way:

echo "primeira linha do arquivo" >> /diretorio/arquivo.txt
echo "segunda linha do arquivo" >> /diretorio/arquivo.txt

Is it possible to put all lines in a single command? Example:

echo "primeira linha
segunda linha
terceira linha
quarta linha
" >> /diretorio/arquivo.txt

But there is something else, I have some variables in my script that I need to be putting in these lines that will be recorded, getting more like this:

variavel1=primeira
variavel2=segunda
variavel3=terceira

echo "$variavel1 linha
$variavel2 linha
$variavel3 linha
quarta linha
" >> /diretorio/arquivo.txt

I’ve searched everywhere, but I can’t find anything related to that.

Answer 1

There are several ways, one is using the command cat and a delimiter:

cat >'arquivo.txt' <<EOT
aí você coloca
um monte de texto
e só precisa terminar
com o a mesma string usada
no delimitador.
EOT

Another is using a function within the Bash:

function coisas_a_imprimir(){
    echo "a"
    echo "b"
}

coisas_a_imprimir > 'arquivo.txt'

The one I consider the most "clean" in Bash is using a subshell:

saida='arquivo.txt'

let variavel_1=1
let variavel_2=2

( echo "Isto é um exemplo de subshell"
  echo ${variavel_1}
  let variavel_2=3
  echo ${variavel_2} ) >$saida

echo $variavel_2

The only "problem" in this case is the one of scope because the variables created and/or changed within it will not be transferred to the shell main -- see in the example the contents of variavel_2 inside and outside the subshell.

Answer 2

You can use the option -e of echo, which allows them to be placed \n and these are interpreted as line breaks:

echo -e "$variavel1 linha\n$variavel2 linha\n$variavel3 linha\nquarta linha"

Another option is to use the command printf, who also accepts \n for line breaks:

printf "$variavel1 linha\n$variavel2 linha\n$variavel3 linha\nquarta linha"

---

The difference is that the echo adds an "extra" line break at the end (in this case, after "fourth line"), while printf no (this would need to have a \n explicit at the end).

You can do the echo do not add line break at the end with option -n:

echo -ne "$variavel1 linha\n$variavel2 linha\n$variavel3 linha\nquarta linha"

There are still other differences between these two commands, and you can see this link for more details.

Answer 3

You can use exec:

#!/bin/bash

exec 1>> text.txt


#Echos

echo "foo"
echo "bar"