[SOLVED] subtraction a list of number

mmhs · 03-17-2012, 06:56 AM

hi guys

i have a file which list some numbers

this file is like

Quote:

2
3
4
5
7
123
43
45
656
435
345
123
5235
.
.
.
.
.

i want to subtract all numbers with 1

i wrote a for loop

Quote:

for i in `cat number.txt`; do $i=$(($i-1));done >> sub.txt

but i gave an error

how can i solve this problem

druuna · 03-17-2012, 07:07 AM

Hi,

Try this:

Code:

for i in $(cat number.txt ); do let i=i-1 ; echo $i ; done

This might clear things up: Bash - ArithmeticExpression

Hope this helps.

mmhs · 03-17-2012, 07:26 AM

Quote:

Originally Posted by druuna

Hi,

Try this:

Code:

for i in $(cat number.txt ); do let i=i-1 ; echo $i ; done

This might clear things up: Bash - ArithmeticExpression

Hope this helps.

thx man for help but it gives ")syntax error: operand expected (error token is "

druuna · 03-17-2012, 07:29 AM

Hi,

Quote:

Originally Posted by mmhs

thx man for help but it gives ")syntax error: operand expected (error token is "

Not on my side:

Code:

$ cat number.txt 
2
3
4
5
7
123
43
45
656
435
345
123
5235
$ for i in $(cat number.txt ); do let i=i-1 ; echo $i ; done
1
2
3
4
6
122
42
44
655
434
344
122
5234

Is the input file a normal text file? (file number.txt to check).

druuna · 03-17-2012, 07:51 AM

Solved?

What did you do to accomplish that (might be of interest for people that stumble upon this thread).

grail · 03-17-2012, 10:41 AM

Just as slight alternative:

Code:

for i in $(< number.txt);do echo $((--i));done

David the H. · 03-17-2012, 02:11 PM

Please use [code][/code] tags around your code and data, to preserve formatting and to improve readability. Please do not use quote tags, colors, or other fancy formatting.

Don't Read Lines With For. You should almost always use a while+read loop instead when working with files or the output of commands.

One possibility it's failing could be line endings. If the file was created on a Windows machine, it will have dos-style cr+lf line endings, instead of unix-style lf-only line endings, and the extra carriage return could be messing it up. This is particularly true in an arithmetic context, since anything not an integer would break syntax.

The output of file will tell you if it has crlf line endings. If so, there are many options for fixing them, such as tofrodos. Google or LQ search it.

mmhs · 03-17-2012, 02:33 PM

Quote:

Originally Posted by druuna

Solved?

What did you do to accomplish that (might be of interest for people that stumble upon this thread).

your script worked perfect however it gave error !!!!

grail · 03-17-2012, 11:53 PM

Let me just look up my crystal ball to help solve that error???