Examples of ${}, #, # #,%, percent of% in the shell

Description

I believe that in the work, many friends in the use of shell scripts encountered ${},%, #等这些字符的使用, and occasionally they will be dizzy, and then I use the following example to let everyone very well remember the Shell ${}, # #和 percent use, this article gives the results obtained in different cases.

Example

Assuming that a variable is defined, "code as follows":

File=/dir1/dir2/dir3/my.file.txt

Different values can be replaced with ${}, respectively:

${file#*/}: Delete the first/its left string: dir1/dir2/dir3/my.file.txt

${file##*/}: Remove the last/and left string: my.file.txt

${file#*.}  : Remove the first one. And the string to the left: file.txt

${file##*.}  : Remove the last one. And the string to the left: txt

${file%/*}: Remove the last/And right string:/dir1/dir2/dir3

${file%%/*}: Delete the first/its right string: (null value)

${file%.*}: Remove the last one. And the string to the right:/dir1/dir2/dir3/my.file

${file%%.*}: Remove the first one. And the string to the right:/dir1/dir2/dir3/my

"The method of Memory is":

# is to remove the left side (on the keyboard # on the left side)

% is removed to the right (on the keyboard% on the right side)

The single symbol is the minimum match; two symbols are the maximum match

${file:0:5}: Extract the leftmost 5 bytes:/dir1

${file:5:5}: Extracts the 5th byte to the right of 5 consecutive bytes:/DIR2

You can also replace the string in the value of the variable:

${file/dir/path}: Replace the first dir with a path:/path1/dir2/dir3/my.file.txt

${file//dir/path}: Replace all dir with Path:/path1/path2/path3/my.file.txt

Look at the above example, you remember, like this article friends can be forwarded and collection, the question of friends in the comments below comment together!!!

Examples of ${}, #, # #,%, percent of% in the shell