How to quote arguments in Bash

Question

I am trying to output a text file which has MIPS code, however it keeps picking up the arguments and won't write them to the text file.

Code:

function errorMessage() {
echo "You have entered the wrong amount of arguments. The default files will now be used"
echo '#input.txt' > input.txt
"add $s0 $s1 $s2" >> input.txt
"sub $s2 $t0 $t3" >> input.txt
"add $s0 $s1 $z2" >> input.txt
"lw $t1 8($t2)" >> input.txt
"addi $t3 $s0 -9" >> input.txt
"sw $s3 4($t0)" >> input.txt
"lw $t11 70000($s0)'" >> input.txt

}

Results:

 #input.txt    
    add   
    sub   
    add   
    lw  8()    
    addi   -9    
    sw  4()    
    lw  70000()

You should pass the arguments to the function.. What your function called in the code? — Alex
– Alex, Commented May 5, 2017 at 12:10
You need to escape special characters. Try echo "add \$s0 \$s1 \$s2" >> input.txt — acylam
– acylam, Commented May 5, 2017 at 12:13
use single quotes so they don't expand. You also either need echo on every line or just a single redirection > input.txt — 123
– 123, Commented May 5, 2017 at 12:16

Zac R. · Accepted Answer · 2017-05-05 12:23:27Z

1

One way of creating files by writing to them is by using whats called a Here Document.

#!/bin/bash
(
cat <<'EOF'
#input.txt
add $s0 $s1 $s2
sub $s2 $t0 $t3
add $s0 $s1 $z2
lw $t1 8($t2)
addi $t3 $s0 -9
sw $s3 4($t0)
lw $t11 70000($s0)
EOF
) > input.txt

What this does is it takes the text between cat <<'EOF' and EOF and writes it to input.txt. Because the EOF in cat <<'EOF' is quoted, the variables that have a $ before them are not treated as bash variables but rather real text. You can replace the string EOF for anything that you want. You can learn more about Here Documents here: http://tldp.org/LDP/abs/html/here-docs.html.

answered May 5, 2017 at 12:23

Zac R.

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Toby Speight · Accepted Answer · 2017-05-05 12:24:23Z

1

If you mean for $s0 to be output literally, you need to use single-quotes rather than double quotes:

echo 'add $s0 $s1 $s2' >> input.txt

You can improve your script by writing once (using a here-document) rather than reopening input.txt for every line:

function errorMessage() {
echo >&2 "You have entered the wrong amount of arguments. The default files will now be used"
cat <<'END' >input.txt
#input.txt
add $s0 $s1 $s2
sub $s2 $t0 $t3
add $s0 $s1 $z2
lw $t1 8($t2)
addi $t3 $s0 -9
sw $s3 4($t0)
lw $t11 70000($s0)
END
}

answered May 5, 2017 at 12:24

Toby Speight

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