In a bash script, how do I move a line to a new file.

ntubski · 04-28-2011, 01:01 PM

How about using the trap mechanism:

Code:

#!/bin/bash

FILE="$1"

onexit()
{
    grep -vFf downloaded-links.txt "$FILE" > remaining-links.txt \
      && [ $? -le 1 ] && mv remaining-links.txt "$FILE"
    exit
}

trap onexit EXIT

while read -r LINE
do
    if axel --alternate --num-connections=6 "$LINE"; then
	echo
	echo "Succeeded downloading following link $LINE"
	echo "$LINE" >> downloaded-links.txt
	echo
    else
	echo
	echo "Failed downloading following link $LINE"
	echo "$LINE" >> failed-links.txt
	echo
    fi
done < "$FILE"

grail · 04-28-2011, 10:11 PM

@ntubski - So I understand how you are waiting till exit to make the changes, but I believe the bigger issue is that the FILE you are reading
from will be actively changed, according to OP, whilst your loop is running. So in turn your script will not be aware of changes until the script is started again.

ntubski · 04-29-2011, 12:44 PM

Oops, I was confused, second try:

Code:

#!/bin/bash

FILE="$1"

cp "$FILE" remaining-links.txt
touch downloaded-links.txt

while [ -s remaining-links.txt ]
do
    while read -r LINE
    do
        if axel --alternate --num-connections=6 "$LINE"; then
	    echo
	    echo "Succeeded downloading following link $LINE"
	    echo "$LINE" >> downloaded-links.txt
	    echo
        else
	    echo
	    echo "Failed downloading following link $LINE"
	    echo "$LINE" >> failed-links.txt
	    echo
        fi

        if ! diff -q remaining-links.txt "$FILE" ; then
            break
        fi
    done < remaining-links.txt

    grep -vFf downloaded-links.txt "$FILE" > remaining-links.txt

done

grail · 04-29-2011, 11:52 PM

Yes that looks like a better alternative

This appears to address my concerns at least ... let us see what the OP thinks?