将wget输出覆盖到文本文件

Question

I'm trying to write wget command's filtered output to a file, but it always appends to the text file and display some unrecognizable characters.

Following script will output on CLI like 1% , 2% and so on nicely but when I redirect the output to a text file, it shows some wired characters and all get appended instead of getting overwritten.

#!/bin/sh
download()
{
    local url=$1
    wget --progress=dot $url 2>&1 | grep --line-buffered "%" | \
        sed -u -e "s,\.,,g" | awk '{printf("\b\b\b\b%4s", $2)}'
    echo " DONE"
}

file="$1"
echo -n "Downloading $file:"
download "$file" > file.log

I tried using > won't work, where am I doing wrong?

This is what I found on the file.

  1%  2%  3%  5%  6%  7%  9% 9% 10% 11% 13% 13% 13% 14%

but it should be

14%

Just the current progress.

All I'm trying to do is write current file progress ( like 10% ) so I can just read the file and check file progress regularly for fronted purposes.

Answer 1

wget (and many other command line tools) use shell escape sequences to display their progress.

This means they print "0%", then do something, then tell the terminal "overwrite '0%' with '5%'", etc.

When you redirect the output to a file, you see these "overwrite" codes.

Using --progress=dot should solve this; then you don't see any percentages (nor any erase code). Instead, it will print one dot per 1K downloaded and you have to count dots.