How to go over each letter of a word and change it in bash

Question

My code looks like this

foo=`cat $words`
for (( i=0; i<${#foo}; i++ )); do
    new=${foo:$i:1}
    while IFS=read -r line 
    do
        if [[ $new=="#" ]]
        then 
            echo "<rect x="20" y="20" fill="black" />"
        elif [[ $new==[A-Z] ]]
        then
            echo "<rect x="20" y="20" fill="white" />"
        fi
    done < "$new"
done

I get an error message containing the following

crossword: line 21: F: No such file or directory
2       crossword: line 21: G: No such file or directory
3       crossword: line 21: #: No such file or directory
4       crossword: line 21: 
5       : No such file or directory
6       crossword: line 21: Z: No such file or directory
7       crossword: line 21: #: No such file or directory
8       crossword: line 21: E: No such file or directory
9       crossword: line 21:

My desired output should have looked like this

 <rect x="20" y="20" fill="white" />
 <rect x="20" y="20" fill="white" />
 <rect x="20" y="20" fill="black" />

 <rect x="20" y="20" fill="white" />
 <rect x="20" y="20" fill="black" />
 <rect x="20" y="20" fill="white" />

Because the content of the file is

FG#
Z#E

Where # will be replaced by black and the letters with white

It's better to use sed or awk for actual text processing; bash is a decent shell, but doing text manipulation with a shell is not ideal. — Jeff Schaller, Dec 16 '22 at 17:20
What is **it** in the statement `I get an error message that it is not a directory`? Which line of code is associated with that error message? [edit] your question to show the exact error message along with whatever command you executed to produce it. — Ed Morton, Dec 16 '22 at 17:24
What are you intending with `done < "$new"`? `<` needs to be followed by a filename, but `$new` just contains one character from the file. And you do `read -r line`, but never use `$line` for anything. There seems to be no need for the `while` loop at all, the `for` loop should be enough. — Barmar, Dec 16 '22 at 17:27
If you do need the `while` loop, there should be a space between `IFS=` and `read`. And you need single quotes around the argument to `echo`, otherwise the quotes inside the tag will match the delimiter quotes. — Barmar, Dec 16 '22 at 17:29
First thing you need to do is paste this script into shellcheck.net. — Barmar, Dec 16 '22 at 17:30
You're showing us error messages claiming to come from line 21 of a script that's 14 lines long. Please post a minimal, complete script that demonstrates your problem and the error messages from THAT script, not from some other script. — Ed Morton, Dec 16 '22 at 17:37
The error messages are from `< "$new"` as I explained above. You're trying to use each character in the file as the name of an input file to read from. Why are you doing that? — Barmar, Dec 16 '22 at 17:46
Where are the incrementing numbers before each error message coming from? Does the script have `echo $i` that you didn't show us? — Barmar, Dec 16 '22 at 17:47

score 2 · Accepted Answer · answered Dec 16 '22 at 17:33

2

This entire thing can be done with a single sed command:

sed -e 's|#|<rect x="20" y="20" fill="black" />\n|g' -e 's|[A-Z]|<rect x="20" y="20" fill="white" />\n|g' "$words"

answered Dec 16 '22 at 17:33

Barmar

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And what if I want to add 20 to x every time so that it goes like 20 for line one and 40 for line two etc – GJO2 Dec 16 '22 at 17:43
Then you need to use a scripting language with arithmetic. – Barmar Dec 16 '22 at 17:44

Ed Morton · Answer 2 · 2022-12-16T17:35:38.810

We'd need more information to be able to debug whatever problem you're having but here's how to really do what you appear to be trying to do using any awk:

$ cat tst.sh
#!/usr/bin/env bash

awk '
    {
        lgth = length($0)
        for ( i=1; i<=lgth; i++ ) {
            char = substr($0,i,1)
            fill = (char == "#" ? "black" : "white")
            printf "<rect x=\"20\" y=\"20\" fill=\"%s\" />\n", fill
        }
        print ""
    }
' "${@:--}"

$ ./tst.sh file
<rect x="20" y="20" fill="white" />
<rect x="20" y="20" fill="white" />
<rect x="20" y="20" fill="black" />

<rect x="20" y="20" fill="white" />
<rect x="20" y="20" fill="black" />
<rect x="20" y="20" fill="white" />

or maybe:

$ cat tst.sh
#!/usr/bin/env bash

awk '
    {
        lgth = length($0)
        for ( i=1; i<=lgth; i++ ) {
            char = substr($0,i,1)
            fill = ""
            if ( char == "#" ) {
                fill = "black"
            }
            else if ( char ~ /[A-Z]/ ) {
                fill = "white"
            }
            if ( fill != "" ) {
                printf "<rect x=\"20\" y=\"20\" fill=\"%s\" />\n", fill
            }
        }
        print ""
    }
' "${@:--}"

,p>

$ ./tst.sh file
<rect x="20" y="20" fill="white" />
<rect x="20" y="20" fill="white" />
<rect x="20" y="20" fill="black" />

<rect x="20" y="20" fill="white" />
<rect x="20" y="20" fill="black" />
<rect x="20" y="20" fill="white" />

How to go over each letter of a word and change it in bash

2 Answers2