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Old 09-26-2008, 11:23 PM   #1
hocheetiong
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Smile How to write a simple BASH script to "test if have folowing files, than delete."?


Hi, i need to write a BASH script to test if have folowing files(1.txt, 1.doc, 2.txt, 2.doc) then delete them.I have try to write:

#!/bin/bash
....
if [ -e 1.*,2.* ]; then
rm 1.* 2.*
fi
....

But got errors?
 
Old 09-26-2008, 11:41 PM   #2
jschiwal
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You could simply delete them. If they don't exist, you just get an error message which you can send to /dev/null.

if [ -f 1.txt ]; then rm 1.txt; fi

You could also use:
[ -f 1.txt ] && rm 1.txt

The command after && (and) is executed if the last command or test before it returned true.

There are many tests. Type in "help test" in the terminal. One thing you need to know. The [ character is actually a command. This is a posix requirement. It is a built in and a command in /usr/bin/[. Enter "which [" and "type [" to see for yourself. This means that you need a space after the [ character. Otherwise bash will look for a "[-f" command which does't exist.

The -e or -f tests take only one argument. If you want to delete these files only if they all exist, you could do:
[ -e 1.txt -a -e 2.txt -a -e 3.txt ] && rm 1.txt 2.txt 3.txt

If you want to delete any of these that exists then you can iterate over the files:
for file in {1..3}.txt; do
[ -f $file ] && rm $file
done

Last edited by jschiwal; 09-27-2008 at 09:24 AM. Reason: typo
 
Old 09-27-2008, 12:12 AM   #3
hocheetiong
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Smile rm 2.txt > /dev/null ,if the file 2.txt is not exist, i dont want to show error msg,

Thank jschiwal reply my question.

I have write a script:

rm 2.txt > /dev/null

If i have this file "2.txt" than will not prompt out error message, but if dont have this file "2.txt" then prompt out error message: rm: remove regular empty file '2.cap' , I already put >/dev/null why still prompt out error message from screen?
 
Old 09-27-2008, 01:49 AM   #4
salasi
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Can you just explain the question a bit more. Is it:
  • delete any of the files, 1.txt, 1.doc, 2.txt, 2.doc..., that exist
or
  • if, and only if, a complete set of files from 1.txt, 2.txt,...n.txt exist, delete all of that set (and similarly ?.doc)

I've got the impression that you can say that if n.txt exists, n.doc will always exist, but that may be me over-interpreting.

Also, are these the only files in the directory, so could you, theoretically, delete *.txt (or ?.txt) and would that be safe? (Presumably, however, you do want to do something to prevent your script being applied to a different directory where thse conditions may not apply.)

And, given that this part of your problem, at least, is easy enough to do in bash is there a good reason that you are doing it in basic?
 
Old 09-27-2008, 04:04 AM   #5
Mr. C.
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Add the -f option to rm. The message prompt you are seeing is printed on STDERR (which has not been redirected).

Last edited by Mr. C.; 09-30-2008 at 11:26 AM.
 
Old 09-30-2008, 09:14 AM   #6
PAix
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Quote:
rm 2.txt > /dev/null

If i have this file "2.txt" than will not prompt out error message, but if dont have this file "2.txt" then prompt out error message: rm: remove regular empty file '2.cap' , I already put >/dev/null why still prompt out error message from screen?
To redirect the error output you would need to write:
Quote:
rm 2.txt 2> /dev/null
The 2> represents stderr output redirection. I hope this makes it a little clearer what is happening. The detail is HERE.
 
Old 09-30-2008, 01:10 PM   #7
jan61
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Moin,

that's not enough. Additionally (look at the post from Mr.C.) you have to add the -f option. The stderr output you see is a prompt - rm wants to know, if you want to remove a file, for which you don't have write permission. You then have to confirm to remove the file. The -f (force) option prevents you from being asked.

Jan
 
Old 09-30-2008, 05:58 PM   #8
PTrenholme
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I don't think you actually need a script to do what you wanted to do, Consider this:
Code:
$ cd tmp
$ touch 1.txt 2.txt 3.txt
$ ls *.txt
1.txt  2.txt  3.txt
$ ls ?.txt
1.txt  2.txt  3.txt
$ ls [0-9].txt
1.txt  2.txt  3.txt
$ rm -f [0-9].txt
$ ls *.txt
ls: cannot access *.txt: No such file or directory
 
Old 10-02-2008, 07:31 AM   #9
jschiwal
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There is one form that you might want to become familiar with. Suppose that you want to copy or move files in a script, from one directory to another, but don't want to overwrite any files. You can use the -i option and automatically supply an answer:
cp -i dir1/*.mp3 dir2/ < <(yes n)
 
Old 10-01-2009, 08:39 AM   #10
pedro.branco
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Quote:
Originally Posted by hocheetiong View Post
Hi, i need to write a BASH script to test if have folowing files(1.txt, 1.doc, 2.txt, 2.doc) then delete them.I have try to write:

#!/bin/bash
....
if [ -e 1.*,2.* ]; then
rm 1.* 2.*
fi
....

But got errors?

What errors are you getting?

if [ -f $1 ]; then
echo "File exists"
else
echo "File not Found"
fi

Works..

Another way.. use test.
 
Old 10-01-2009, 12:17 PM   #11
PTrenholme
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Quote:
Originally Posted by pedro.branco View Post
. . .
Another way.. use test.
Just a F.Y.I.: On many systems, " [ " is an alias for "test," and " ] " is ignored. (Note that the blanks around the square brackets are part of the alias command name.) On almost all other systems, the " [ " and " ] " are hard-coded into bash, and "test" is provided a a separate program for those (very rare) occasions when "test" is needed from some non-bash program.
 
  


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