How do I create a new empty file in a bash script?

Question

I'm running some third-party Perl script written such that it requires an output file for the output flag, -o.

Unfortunately, the script appears to require an actual file, that is, users must create an empty file filename.txt with 0 bytes and then input this empty file on the script command line

perl script1.pl -o filename.txt

Question: How would I create an empty file within a bash script? If one simply tries perl script1.pl -o filename.txt, the script gives an error that the file doesn't exist.

Possible duplicate of How to create a simple .txt (text) file using terminal? — don_crissti, Feb 08 '17 at 22:22

score 45 · Accepted Answer · answered Feb 08 '17 at 20:11

45

Use touch command. touch filename.txt.

answered Feb 08 '17 at 20:11

MKT

5,951

22

echo -n >file – Hannu Feb 08 '17 at 21:48
14

take care - this will not empty your file if it already exists – johanvdw Jun 25 '18 at 11:30
1

Actually I tried touch and "echo -n > file" inside my bash script but I get an error when I execute the script: "No such file or directory" on that line. Can someone help please? – andrewz Mar 05 '20 at 21:07
5

echo -n "" > filename will empty the file if it exists or creates a file if it doesn't exist. – Vituvo Mar 18 '20 at 09:09

Sapphire_Brick · Answer 2 · 2020-10-30T20:41:04.380

15

The shortest way:

>filename

edited Oct 30 '20 at 20:41

answered Oct 30 '20 at 04:17

Sapphire_Brick

321

2

Best answer. Couldn't be shorter. – DevonDahon Dec 17 '20 at 16:46
Could you provide a reference to an explanation, please? – Alexey Oct 08 '22 at 12:52
1

it's related to redirecting output on bash ‣ [n]>[|]word – manus Apr 18 '23 at 03:32

score 12 · Answer 3 · answered Feb 08 '17 at 20:13

12

Use the null command (:) redirect (> filename) trick (:>), as this will truncate to zero or create the named file.

$ echo foo > filea
$ :> filea
$ wc -c filea
       0 filea
$ rm filea
$ :> filea
$ wc -c filea
       0 filea

(This will fail if the shell sets a NOCLOBBER option.)

answered Feb 08 '17 at 20:13

thrig

34,938

1

If noclobber is set, use the redirection >| to clobber, so :>| filea -- documented in the manual – glenn jackman Feb 08 '17 at 20:21
4

Just > filename.txt would do, no need for the :. Or >> filename.txt if we don't want to trash it if it does happen to exist. – ilkkachu Feb 08 '17 at 21:57
3

@ilkkachu although the question does specify Bash, using : does make the script more likely to accomplish its task with other shells e.g. Zsh. – can-ned_food Feb 19 '17 at 09:22

score 3 · Answer 4 · answered Feb 08 '17 at 20:51

You could always use perl, too.

$ stat filename.txt
stat: cannot stat 'filename.txt': No such file or directory
$ perl -e 'open($fh,">","filename.txt") or die $!;close($fh)'                                         
$ stat filename.txt                                                                                   
  File: 'filename.txt'
  Size: 0           Blocks: 0          IO Block: 4096   regular empty file
Device: 801h/2049d  Inode: 280728      Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/ xieerqi)   Gid: ( 1000/ xieerqi)
Access: 2017-02-08 13:51:01.479121995 -0700
Modify: 2017-02-08 13:51:01.479121995 -0700
Change: 2017-02-08 13:51:01.479121995 -0700
 Birth: -

score 1 · Answer 5 · answered Jul 29 '21 at 14:48

dd can be used to create an empty file as follows:

dd if=/dev/null of=filename.txt count=0

One case where dd is more useful than the other approaches is creating an EFI variable (PK) through the efivars filesystem (/sys/firmware/efi/efivars).

One some platforms and Linux distributions, the file is created with the "immutible" attribute set (shows up as the "i" flag with "lasattr"). So, any subsequent operations on the file fail.

For example, touch not only creates the file, but sets the time stamp on the file. Similarly, piping to the file with > not only creates the file, but performs additional operations that fail. The dd command does not appear to fail the same way.

How do I create a new empty file in a bash script?

5 Answers5