Following is an example of appending "Arju" keyword to each words within brace at first and " always." keyword appends to each words within brace at last.
$ echo 'Arju '{'GoodBoy','Goes to university','Works'}' always. '
Arju GoodBoy always. Arju Goes to university always. Arju Works always.
- With combination of brace and and cat command we can concatenate several files contents into one. Following is an example.
$ cat >file1.txt
one
$ cat >file2.txt
two
$ cat >file3.txt
three
$ cat {file1.txt,file2.txt,file3.txt} >file5.txt
$ cat file5.txt
one
two
three
- We can take facility of brace expansion while move or copy or rename files. For example the following can be used to rename a .txt file to .bak file.
$ cat file5.txt
one
two
three
$ mv file5.{txt,bak}
$ cat file5.bak
one
two
three
- Note that no spaces are allowed within the braces unless the spaces are quoted or escaped.
- With double dot we can use extended brace expansion construction which is a feature introduced in version 3 of Bash.
Example:
$ echo {a..m}
a b c d e f g h i j k l m
$ echo {5..10}
5 6 7 8 9 10
- The {} double curly brackets are a placeholder for output text. For example, curly brackets are placeholder for the path name output by "find".
DELETE_DIR=/home/arju/junk
find "$DELETE_DIR" -type f -atime +30 -exec rm {} \;
The above script deletes the files from "/home/arju/junk" that have not been accessed in at least 30 days (plus sign ... +30).
where,
-type indicates filetype", and
f = regular file
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More succinctly,
ReplyDeletecat {file1.txt,file2.txt,file3.txt} >file5.txt
can be rewritten as
cat file{1,2,3}.txt > file5.txt