replace within string variable aka bash substitution

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bash replace sh string subst substitute substitution variable variables

### delete shortest match at "^":
### ../hmm -> ./hmm 
echo ${path#.}

### delete longest match at "^":
### ../hmm -> /hmm 
echo ${path##.}

### delete shortest match at "$":
### /hmm// -> ./hmm/ 
echo ${path%/}

### delete longest match at "$":
### /hmm// -> /hmm 
echo ${path%%/}

### replace once:
### dir/subdir/file -> dir\/subdir/file
echo ${path/\//\\/}

# ### replace globally:
# ### dir/subdir/file -> dir\/subdir\/file
#echo ${path//\//\\/}

# ### replace slash at "^":
# ### /absolute/path -> relative/path
#echo ${path/#\///}

# ### replace slash at "$":
# ### /path/to/ -> /path/to
#echo ${path/%\///}

# ### split string at first "/":
# ### /path/to/ -> path/to/
echo ${path#*/}