I am using

a=`head -1 Rt.in` 

to get first value from my file and I am saving it as a variable then I am using same variable to tail -$a to tail last lines from my input. But it is giving an error:

tail: illegal option -- -53\r.

My input file has 4 columns from the third row onwards.

Here is a part of script I am using :

a=`head -1 Rt.in`
echo $a
tail -$a Rt.in

and the error in output I am getting is this:

tail: illegal option -- -53\r

And the part of input file is as follows:

H    9.155963    1.289174   11.531518
H    9.004353    2.726286   11.683448
N   11.762550    3.890769   11.785241
N   10.610393    3.635048    9.544268
N   10.745642    1.175050    9.076323
N   13.210069    2.309946    9.848128
N   12.319480    0.955257   11.800435
C   12.359945    3.942548   12.929277
C   11.267322    5.027779   11.274755
H    9.052185    4.031311    6.865735
C   10.031631    3.303244    8.416945
C   10.093512    1.894663    8.164740
C    9.546565    1.312421    7.090592

There are 53 such lines.

Can anybody will tell me why I am getting this error and how can I remove it??
If I run above script using pipes directly in terminal I am getting error as tail: -: No such file or directory and then list of few atoms.

  • Your Rt.in file was probably created on Windows. Use dos2unix to create a new file that Unix tools will understand. Nov 4 '15 at 10:57
  • dking, if you need to edit your question to add the '53' at the top of the input file, click the edit link at the bottom-left of it, or this copy
    – Jeff Schaller
    Nov 4 '15 at 13:57
  • Hi i did not create this file on windows i created it on mac
    – dking
    Dec 11 '15 at 12:21

The number of lines should not be the parameter it should be:

tail -n $a Rt.in

Now you get the number of last lines that is defined in the first line of your file. This -n should also be used with your head command.

  • Yes i tried that too but it is giving error tail: illegal offset -- 53\r.
    – dking
    Nov 4 '15 at 10:45
  • Can anybody edit my question there is 53 at the beginning of my input file
    – dking
    Nov 4 '15 at 10:47
  • tail -5 and head -9 (using whatever digits) work and are the original options for these commands and still work. These options are no longer documented for some reason unknown to me.
    – RobertL
    Nov 4 '15 at 11:14
  • @dking the answer is in the comment on your question. You have incorrect line endings on Rt.in probably because it was created on Windows.
    – RobertL
    Nov 4 '15 at 11:26
  • @RobertL - this answer is correct. you should review the standard, use -n.
    – mikeserv
    Nov 4 '15 at 14:31

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