Extract filename and extension in Bash

Question

I want to get the filename (without extension) and the extension separately.

The best solution I found so far is:

NAME=`echo \"$FILE\" | cut -d\'.\'          


        

Answer 1

The accepted answer works well in typical cases, but fails in edge cases, namely:

• For filenames without extension (called suffix in the remainder of this answer), extension=${filename##*.} returns the input filename rather than an empty string.
• extension=${filename##*.} does not include the initial ., contrary to convention.
  • Blindly prepending . would not work for filenames without suffix.
• filename="${filename%.*}" will be the empty string, if the input file name starts with . and contains no further . characters (e.g., .bash_profile) - contrary to convention.

---------

Thus, the complexity of a robust solution that covers all edge cases calls for a function - see its definition below; it can return all components of a path.

Example call:

splitPath '/etc/bash.bashrc' dir fname fnameroot suffix
# -> $dir == '/etc'
# -> $fname == 'bash.bashrc'
# -> $fnameroot == 'bash'
# -> $suffix == '.bashrc'

Note that the arguments after the input path are freely chosen, positional variable names.
To skip variables not of interest that come before those that are, specify _ (to use throw-away variable $_) or ''; e.g., to extract filename root and extension only, use splitPath '/etc/bash.bashrc' _ _ fnameroot extension.

---

# SYNOPSIS
#   splitPath path varDirname [varBasename [varBasenameRoot [varSuffix]]] 
# DESCRIPTION
#   Splits the specified input path into its components and returns them by assigning
#   them to variables with the specified *names*.
#   Specify '' or throw-away variable _ to skip earlier variables, if necessary.
#   The filename suffix, if any, always starts with '.' - only the *last*
#   '.'-prefixed token is reported as the suffix.
#   As with `dirname`, varDirname will report '.' (current dir) for input paths
#   that are mere filenames, and '/' for the root dir.
#   As with `dirname` and `basename`, a trailing '/' in the input path is ignored.
#   A '.' as the very first char. of a filename is NOT considered the beginning
#   of a filename suffix.
# EXAMPLE
#   splitPath '/home/jdoe/readme.txt' parentpath fname fnameroot suffix
#   echo "$parentpath" # -> '/home/jdoe'
#   echo "$fname" # -> 'readme.txt'
#   echo "$fnameroot" # -> 'readme'
#   echo "$suffix" # -> '.txt'
#   ---
#   splitPath '/home/jdoe/readme.txt' _ _ fnameroot
#   echo "$fnameroot" # -> 'readme'  
splitPath() {
  local _sp_dirname= _sp_basename= _sp_basename_root= _sp_suffix=
    # simple argument validation
  (( $# >= 2 )) || { echo "$FUNCNAME: ERROR: Specify an input path and at least 1 output variable name." >&2; exit 2; }
    # extract dirname (parent path) and basename (filename)
  _sp_dirname=$(dirname "$1")
  _sp_basename=$(basename "$1")
    # determine suffix, if any
  _sp_suffix=$([[ $_sp_basename = *.* ]] && printf %s ".${_sp_basename##*.}" || printf '')
    # determine basename root (filemane w/o suffix)
  if [[ "$_sp_basename" == "$_sp_suffix" ]]; then # does filename start with '.'?
      _sp_basename_root=$_sp_basename
      _sp_suffix=''
  else # strip suffix from filename
    _sp_basename_root=${_sp_basename%$_sp_suffix}
  fi
  # assign to output vars.
  [[ -n $2 ]] && printf -v "$2" "$_sp_dirname"
  [[ -n $3 ]] && printf -v "$3" "$_sp_basename"
  [[ -n $4 ]] && printf -v "$4" "$_sp_basename_root"
  [[ -n $5 ]] && printf -v "$5" "$_sp_suffix"
  return 0
}

test_paths=(
  '/etc/bash.bashrc'
  '/usr/bin/grep'
  '/Users/jdoe/.bash_profile'
  '/Library/Application Support/'
  'readme.new.txt'
)

for p in "${test_paths[@]}"; do
  echo ----- "$p"
  parentpath= fname= fnameroot= suffix=
  splitPath "$p" parentpath fname fnameroot suffix
  for n in parentpath fname fnameroot suffix; do
    echo "$n=${!n}"
  done
done

Test code that exercises the function:

test_paths=(
  '/etc/bash.bashrc'
  '/usr/bin/grep'
  '/Users/jdoe/.bash_profile'
  '/Library/Application Support/'
  'readme.new.txt'
)

for p in "${test_paths[@]}"; do
  echo ----- "$p"
  parentpath= fname= fnameroot= suffix=
  splitPath "$p" parentpath fname fnameroot suffix
  for n in parentpath fname fnameroot suffix; do
    echo "$n=${!n}"
  done
done

Expected output - note the edge cases:

• a filename having no suffix
• a filename starting with . (not considered the start of the suffix)
• an input path ending in / (trailing / is ignored)
• an input path that is a filename only (. is returned as the parent path)
• a filename that has more than .-prefixed token (only the last is considered the suffix):

----- /etc/bash.bashrc
parentpath=/etc
fname=bash.bashrc
fnameroot=bash
suffix=.bashrc
----- /usr/bin/grep
parentpath=/usr/bin
fname=grep
fnameroot=grep
suffix=
----- /Users/jdoe/.bash_profile
parentpath=/Users/jdoe
fname=.bash_profile
fnameroot=.bash_profile
suffix=
----- /Library/Application Support/
parentpath=/Library
fname=Application Support
fnameroot=Application Support
suffix=
----- readme.new.txt
parentpath=.
fname=readme.new.txt
fnameroot=readme.new
suffix=.txt

Answer 2

Using example file /Users/Jonathan/Scripts/bash/MyScript.sh, this code:

MY_EXT=".${0##*.}"
ME=$(/usr/bin/basename "${0}" "${MY_EXT}")

will result in ${ME} being MyScript and ${MY_EXT} being .sh:

---

Script:

#!/bin/bash
set -e

MY_EXT=".${0##*.}"
ME=$(/usr/bin/basename "${0}" "${MY_EXT}")

echo "${ME} - ${MY_EXT}"

Some tests:

$ ./MyScript.sh 
MyScript - .sh

$ bash MyScript.sh
MyScript - .sh

$ /Users/Jonathan/Scripts/bash/MyScript.sh
MyScript - .sh

$ bash /Users/Jonathan/Scripts/bash/MyScript.sh
MyScript - .sh

Answer 3

You can use the magic of POSIX parameter expansion:

bash-3.2$ FILENAME=somefile.tar.gz
bash-3.2$ echo "${FILENAME%%.*}"
somefile
bash-3.2$ echo "${FILENAME%.*}"
somefile.tar

---

There's a caveat in that if your filename was of the form ./somefile.tar.gz then echo ${FILENAME%%.*} would greedily remove the longest match to the . and you'd have the empty string.

(You can work around that with a temporary variable:

FULL_FILENAME=$FILENAME
FILENAME=${FULL_FILENAME##*/}
echo ${FILENAME%%.*}

)

---

This site explains more.

${variable%pattern}
  Trim the shortest match from the end
${variable##pattern}
  Trim the longest match from the beginning
${variable%%pattern}
  Trim the longest match from the end
${variable#pattern}
  Trim the shortest match from the beginning

Answer 4

$ F = "text file.test.txt"  
$ echo ${F/*./}  
txt  

This caters for multiple dots and spaces in a filename, however if there is no extension it returns the filename itself. Easy to check for though; just test for the filename and extension being the same.

Naturally this method doesn't work for .tar.gz files. However that could be handled in a two step process. If the extension is gz then check again to see if there is also a tar extension.

Answer 5

You can use basename.

Example:

$ basename foo-bar.tar.gz .tar.gz
foo-bar

You do need to provide basename with the extension that shall be removed, however if you are always executing tar with -z then you know the extension will be .tar.gz.

This should do what you want:

tar -zxvf $1
cd $(basename $1 .tar.gz)

Answer 6

You can force cut to display all fields and subsequent ones adding - to field number.

NAME=`basename "$FILE"`
EXTENSION=`echo "$NAME" | cut -d'.' -f2-`

So if FILE is eth0.pcap.gz, the EXTENSION will be pcap.gz

Using the same logic, you can also fetch the file name using '-' with cut as follows :

NAME=`basename "$FILE" | cut -d'.' -f-1`

This works even for filenames that do not have any extension.