0

I have a file look like:

login1.stampede(73)$ cat mc_input 
800  ! n_pass
300  ! n_equil_pass
6 6 6 ! simulation cell dimension in x, y, and z
700   ! Tinit
100   ! Tmin
700   ! Tmax
-10   ! Tinc
Li -6 Fe 0   ! mu init
Li -6  Fe 0  ! mu min
Li 6    Fe 0  ! mu max
Li 0.3  Fe 0  ! mu inc
  4  ! number of increments between structure output (0 indicates no output)
  1  ! calculate average correlations yes(1) or no (0)
  0  ! temp_chem = 0 if temperature runs 1 if chem runs

now I would like to target the line 

Li -6 Fe 0   ! mu init

and replace -6 with another mu_init=-3, how could I achieve it with sed? thank you. Therefore the result should be :

Li -3 Fe 0   ! mu init

and "Fe 0" can be all kinds of other element-number combination and we will keep it fixed, for example "H 2", "Ge 3.2"

what i currently have is:

 sed -i 's,^\(Li \).*! mu init,\1$mu_init'  Fe 0   ! mu init',' mc_input

but it does not work....

Improve this question
3
  • It is not clear what your selection criteria from the original file ? From your sed command, it looks like you are looking for a line starting with (Li), which I do not see in your source file. You need to a little more specific. Commented Mar 25, 2016 at 13:55
  • You need to clarify. Is the line you seek always going to be exactly like the sample, or are you targeting all lines beginning with 'Li'? Commented Mar 25, 2016 at 13:59
  • Hi, I am targeting lines start with Li and then some number and then some other element and number and then ends with "! mu init"... So something looks like Li #number# #another element# #another number# ! mu init Commented Mar 25, 2016 at 14:16

1 Answer 1

Reset to default
1

New tested version after your comment about -3.333:

sed -i "s/^\(Li \)[0-9-][.0-9-]*\(.*mu init\)/\1${mu_init}\2/" mc_input

- - - -

For reference the first tested version:

sed -i "s/^\(Li \)[0-9-][0-9-]*\(.*mu init\)/\1${mu_init}\2/" mc_input

Some , in your version have been replaced with /.

See also other modifications: double quotes, variable, etc.

Improve this answer
5
  • this works... may i ask if ^(Li ) means Line start with Li but do not change during substitution and *(.*mu init) means ending with mu init and [0-9-][0-9-] means the number immediately after "Li "? Thank you Commented Mar 25, 2016 at 14:27
  • ^(LI ) means both starts with Li<space> and it can be referenced in the replacement with \1. (.* mu init) means both any sequence of chars terminating with mu init and it can be referenced in the replacement with \2. [0-9-][0-9-] means any combination of - and digit with 2 chars after Li<space>. Commented Mar 25, 2016 at 14:38
  • I see.... Thank you so much, ehm, there is one tricky thing here, For Li -6, it might be Li - 3.333 as well.... do we have anyway to treat this situations, not limiting 2 chars digit? thank you. Commented Mar 25, 2016 at 14:43
  • Thank you so much. So [0-9-][.0-9-] means any decimal number of any length ? Thank you. Commented Mar 25, 2016 at 14:51
  • hem it means more: any sequence of chars starting with - or a digit, followed with 0 or more chars in ( digit or . or -), a mix of these. Commented Mar 25, 2016 at 15:09

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.