Question

I would like to change lowercase filenames to uppercase with awk/sed/bash

your help would be appreciated

aaaa.txt
vvjv.txt
acfg.txt

desired output

AAAA.txt
VVJV.txt
ACFG.txt

Answer 1

PREFACE:

If you don’t care about the case of your extensions, simply use the ‘tr’ utility in a shell loop:

for i in *.txt; do mv "$i" "$(echo "$i" | tr '[a-z]' '[A-Z]')"; done

If you do care about the case of the extensions, then you should be aware that there is more than one way to do it (TIMTOWTDI). Personally, I believe the Perl solution, listed here, is probably the simplest and most flexible solution under Linux. If you have multiple file extensions, simply specify the number you wish to keep unchanged. The BASH4 solution is also a very good one, but you must be willing to write out the extension a few times, or alternatively, use another variable to store it. But if you need serious portability then I recommend the last solution in this answer which uses octals. Some flavours of Linux also ship with a tool called rename that may also be worth checking out. It’s usage will vary from distro to distro, so type man rename for more info.

SOLUTIONS:

Using Perl:

# single extension
perl -e 's/\.[^\.]*$/rename $_, uc($`) . $&/e for @ARGV' *.txt

# multiple extensions
perl -e 's/(?:\.[^\.]*){2}$/rename $_, uc($`) . $&/e for @ARGV' *.tar.gz

---

Using BASH4:

# single extension
for i in *.txt; do j="${i%.txt}"; mv "$i" "${j^^}.txt"; done

# multiple extensions
for i in *.tar.gz; do j="${i%.tar.gz}"; mv "$i" "${j^^}.tar.gz"; done

# using a var to store the extension:
e='.tar.gz'; for i in *${e}; do j="${i%${e}}"; mv "$i" "${j^^}${e}"; done

---

Using GNU awk:

for i in *.txt; do

    mv "$i" $(echo "$i" | awk '{ sub(/.txt$/,""); print toupper($0) ".txt" }');
done

Using GNU sed:

for i in *.txt; do

    mv "$i" $(echo "$i" | sed -r -e 's/.*/\U&/' -e 's/\.TXT$/\u.txt/');
done

---

Using BASH3.2:

for i in *.txt; do

    stem="${i%.txt}";

    for ((j=0; j<"${#stem}"; j++)); do

        chr="${stem:$j:1}"

        if [[ "$chr" == [a-z] ]]; then

            chr=$(printf "%o" "'$chr")

            chr=$((chr - 40))

            chr=$(printf '\'"$chr")
        fi

        out+="$chr"
    done

    mv "$i" "$out.txt"

    out=
done