Bash: For Filename do......

Question

Hi I'm not used to do things in Bash, so I'm having some problems:

My goal is to look for special files in a folder, and if found generate some other files with the same filenames, but different extension.

Something like:

For Files-that-are-called-"SysBackup*.Now" 
do
  NewFileName = ChangeFileExt(FoundFilename),BK
  GenerateNewfile(NewFileName)
done

The above is of course dummycode, I won't bother you with the code I have done, as it is not working :-)

So the goal should be:

If the folder contains Sysbackup123.now and Sysbackup666.now, I will end up with the files Sysbackup123.bk and Sysbackup666.bk

Thank you for any help

Michael

Answer 1

You could do something like this:

for F in SysBackup*.Now; do
    [ -f $F ] && touch $(echo "$F" | sed 's/Now$/BK/')
done

This uses echo to pass the filenames to sed, which changes the postfix string "Now" to "BK". touch creates the file, if it does not exist yet. The new file will be empty. The test [ -f $F ] ensures that only files (not directories or symlinks) are considered.

Alternatively, you can use find. An example using basename, as demonstrated in Stephen Darlington's answer:

find . -type f -iname "SysBackup*.Now" -exec sh -c "touch \$(basename '{}' .Now).BK" \;

Note that in both examples it is important to place quotes around the filenames, to ensure proper handling of filenames with spaces.

Answer 2

Fairly straightforward:

for a in Sysbackup*.now;
do
  [ -f $a ] && touch $(basename $a .now).bk ;
done

Answer 3

This is how I do it with sh:

#!/bin/sh

for file in SysBackup*.now; do
  if [ ! -e "$file" ]; then
    continue
  fi

  base=${file##*/}
  bk=${base%.now}.bk

  touch $bk
done

Answer 4

Here's another way to do the substitution. Bash has an equivalent to sed's s/string1$/string2/ which uses the regex dollar sign to select the end of the pattern:

for a in Sysbackup*.Now;
do
  [ -f $a ] && touch "${a/%.Now/.BK}"
done

The percent sign matches at the end and a pound (#) matches at the beginning.

Answer 5

here's another way, if you don't want to use for loop and testing whether its a file or not

find /path -maxdepth 1 -type f -name "Sysbackup*now" | while read file
do
  touch "${file/%.now/.bK}"
done