optipng: Error: Can't back up the existing output file

1.0 Error

While running optipng on a png file, the following error was obtained,

Error: Can't back up the existing output file

2.0 Solution

The file was not having the write permission. Once, the write mode bit for the file was set, optipng worked fine.

$ ls -ls abc.png 84 -r--r--r-- 1 alice dev 82981 Jan 30 05:04 abc.png $ optipng abc.png ** Processing: abc.png 1024x512 pixels, 3x8 bits/pixel, RGB Error: Can't back up the existing output file ** Status report 1 file(s) have been processed. 1 error(s) have been encountered. $ chmod +w abc.png $ optipng abc.png ** Processing: abc.png 1024x512 pixels, 3x8 bits/pixel, RGB Input IDAT size = 82884 bytes Input file size = 82981 bytes Trying: abc.png is already optimized.

Software: