Why Regex doesn't work in bash/ksh while it works fine in command line-CodePudding

I want to exclude any files ending with '.ses' or files with no extension using the following regex pattern. It works fine in command line but not in a shell (bash/ksh).

Regex pattern: "\\\.(?!ses\$)([^.] \$)"

File name examples:

"/test/path/test file with spaces.__1" (expected true)
"/test/path/test file with spaces.ses" (expected false)
"/test/path/test file with spaces" (expected false)
"/test/path/test file with spaces.txt" (expected true)

FILE_NAME="/test/path/test file with spaces.__1"

PATTERN_STR="\\\.(?!ses\$)([^.] \$)"

if [[ "${FILE_NAME}" =~ ${PATTERN_STR} ]]; then

        Match_Result="true"
else

        Match_Result="false"

fi

echo $Match_Result

it returns "true" but "false" in the shell. Anyone knows why?

CodePudding user response：

I would just use a case statement with suitable globs:

case "${FILE_NAME##*/}" in
*.ses)
    Match_Result=false
    ;;
*.*)
    Match_Result=true
    ;;    
*)
    Match_Result=false
    ;;
esac

I would use an array instead of doing whitespace gymnastics.

CodePudding user response：

You can reverse your logic and fail all strings that contain .ses at the end or do not contain a dot after the last /.

Then, you can use this script:

#!/bin/bash
declare -a arr=("/test/path/test file with spaces.__1"
"/test/path/test file with spaces.ses"
"/test/path/test file with spaces"
"/test/path/test file with spaces.txt")
# true false false true
PATTERN_STR='(/[^/.] |\.ses)$'
for FILE_NAME in "${arr[@]}"; do
  if ! [[ "$FILE_NAME" =~ $PATTERN_STR ]]; then
    Match_Result="true"
  else
    Match_Result="false"
  fi
  echo $Match_Result
done;

Output:

true
false
false
true

Details:

( - start of a capturing group:
- /[^/.] - / and then one or more chars other than / and .
| - or
- \.ses - .ses
) - end of grouping
$ - end of a string.

A case insensitive version is enabled with shopt -s nocasematch/shopt -u nocasematch (see Case insensitive regex in Bash).