Is this sed command valid?

January 15, 2022

I have 2 lines of sed that I have trouble understanding

I understand that the syntax of sed is :

sed OPTIONS [SCRIPT] [INPUTFILE]

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but in this command below there is no input file I am just curious what this is doing, any help is very much appreciated

$(echo $d | sed 's/.*\///g')#

cat /kaldi/README | sed "s/akiplaner/${n}/g" >  extracted/$nf/etc/README #

*note : below is the whole code

for d in /dir1/dataset/audios/*; do
    echo $d
    n=$(echo $d | sed 's/.*\///g') #
    nf=${n}
    echo $n $a $nf
    mkdir -p extracted/$nf/wav
    mkdir -p extracted/$nf/etc
    rm -f extracted/$nf/etc/prompts-original
    rm -f extracted/$nf/etc/PROMPTS
    cat /kaldi/README | sed "s/akiplaner/${n}/g" >extracted/$nf/etc/README #

    for f in $d/*.wav; do
        n2=$(echo $f | sed 's/.*\///g')
        n3=$(echo $n2 | sed 's/\.wav//g') # removing .wav from $n2 string
        echo $n2
        echo $n3
        cp $f extracted/$nf/wav/$n2
        #sox --vol 0.01 $f -t wav extracted/$nf/wav/$n2;
        normalize-audio -a 0.3 extracted/$nf/wav/$n2

        cp $d/$n3.txt temp.txt

        echo "$n3 $(cat temp.txt)" >>extracted/$nf/etc/prompts-original
        echo "${nf}/mfc/${n3} $(cat temp.txt)" >>extracted/$nf/etc/PROMPTS
    done
    a=$(($a + 1))
done

>Solution :

there is no input file I am just curious what this is doing

The answer is at your fingertips.

$ LC_ALL=C sed --help
...
... if no input files are
specified, then the standard input is read.

Note: | shell operator connects one command standard output to another command’s standard input. There are surely endless resources on the internet for basic introduction to shell streams and input output operations – it might be a good occasion to research some of them, like https://mywiki.wooledge.org/BashGuide/InputAndOutput .

sed OPTIONS [SCRIPT] [INPUTFILE]

It’s:

$ LC_ALL=C sed --help
Usage: sed [OPTION]... {script-only-if-no-other-script} [input-file]...

The stuff in [...] is optional. ... represents stuff it can be repeated.

There are man problems with the script – it will break on filenames with spaces or newlines in the name or on filenames with * in the name… Remember to check your scripts with shellcheck – it will catch such mistakes.

‘s/.*///g’ am I correct in saying this pattern is removing any file or folder whose name starts with

From a line of text it removes everything .* before a / slash. You can learn regex with fun with https://regexcrossword.com/ and sed here https://www.grymoire.com/Unix/Sed.html .

It’s an odd way of writing basename "$n" and the next line is just basename "$n" .wav.