How to use an input file of non-exact filenames for an operation?

Question

I have a file of filenames for files in a certain directory. However, some of the file names may:

1. Have spaces in the original filename replaced with underscores (so directory/file with spaces becomes file_with_spaces in the input file)
2. May not actually match a file in the directory

If I didn't have these two conditions, I'd use cat inputfile | awk 'commands' to process apply the commands I want on the file. However, I would like for some way to catch filename not found errors and either:

1. Try with different combinations of underscores being replaced with spaces until it finds a matching file
2. Provide a list of files that had no matches, even after substituting spaces for underscores.

Is there a good way to do this? I suspect that some type of script will be needed (rather than a one-line command), but I am not yet familiar with shell scripting enough to think of the solution.

Answer 1

The approach I would use is to take the output of ls, set up an array mapping the converted name back to the original name, then process each line of the input file. If the input is in the array then output the value of the array, otherwise add the input line to the missing file. So something like put this in a file, change to the directory and run it with inputfile as a parameter

#!/usr/bin/awk
# set up an array t of translations
BEGIN {
    while (("ls" | getline )>0) {
        k=$0
        gsub(/ /,"_")
        if ($0 in t) {
            print "$0 matches more than one file" > /dev/stderr
            exit(2)
        }
        t[$0]=k
    }
    close("ls")
}
    { if ($0 in t) {
            print t[$0]
        } else {
            print $0 > "../missing"
        }
    }

Answer 2

Transform the munged file names into patterns that match the original file.

#!/bin/bash
shopt -s nullglob extglob
IFS=$'\n'
while read -r filename; do
  pattern=${filename//\\/\\\\}
  pattern=${pattern//\[/\\\[}
  pattern=${pattern//\(/\\\(}
  pattern=${pattern//\*/\\\*}
  pattern=${pattern//\?/\\\?}
  pattern=${pattern//_/'[ _]'}
  matches=($pattern@())
  case ${#matches[@]} in
    0) echo "No match for $filename";;
    1) echo "$filename found as ${matches[0]}";;
    *) echo "$filename matches ${#matches[@]} files";;
  esac
done <inputfile

Answer 3

With zsh, you could use its approximate matching capability:

approx-cat() {
  emulate -L zsh
  setopt extendedglob nullglob
  local err files
  for ((err = 0; err <= $1; err++)); do
    files=((#a$err)$2)
    case $#files in
      (1) cat -- $files; return;;
      (0) ;;
      (*) echo >&2 "$#files found at error count $err:"
          printf >&2 '  "%s"\n' $files
          return 1;;
    esac
  done
  return 1
}

And call as:

approx-cat 3 'directory/file with spaces'

To allow up to 3 errors in the file name.

Example:

$ approx-cat 3 /ebc/passwds
2 found at error count 2:
  "/etc/passwd"
  "/etc/passwd-"
$ approx-cat 3 /ebc/Issue
Debian GNU/Linux stretch/sid \n \l