sed: remember capture in second expression

Question

I am trying to find occurence of captured pattern and pre-pend next line with captured pattern.

For example:

...
[line 10] #---------- SOLID: tank_phys.0
[line 11]   Shape {
...
[line 22] #---------- SOLID: head_phys.0
[line 23]   Shape {  
...

expected output:

...
[line 10] #---------- SOLID: tank_phys.0
[line 11]   DEF tank Shape {
...
[line 22] #---------- SOLID: head_phys.0
[line 23]   DEF head Shape {   
...

Here is what I have:

sed -rn '/#---------- SOLID: (.*)_phys.0/{n ; s/Shape/DEF <PreviousCapture> Shape/p;}' g4_00.wrl

How can I substitute Shape { with DEF tank Shape { ?

Thanks

GT

Store the result of the first `sed` in a variable, then use that variable in the second `sed`? — Stephen Newell, Mar 27 '18 at 03:56
Please shoe more samples in code tags in your post, it is not clear. — RavinderSingh13, Mar 27 '18 at 04:00
that will not work if I want to process whole file in one go. The file containes multiple occurences of the pattern I showed. thanks . Perhaps if you show me how you were thinking ? — user1301295, Mar 27 '18 at 04:00
works perfect, now makes me feel like I know nothing about sed. thanks — user1301295, Mar 27 '18 at 16:02

Allan · Accepted Answer · 2018-03-27T08:16:32.870

With a pure sed solution:

INPUT:

$ cat file
#---------- SOLID: tank_phys.0
  Shape {
abcdef
1234
#---------- SOLID: head_phys.0
  Shape { 
12345
gdfg

Command:

$ sed -rn '/#---------- SOLID: (.*)_phys.0/{p;s/#---------- SOLID: (.*)_phys.0/DEF \1/;N;s/\n//;s/ {2,}/ /;s/^/  /p;b};/#---------- SOLID: (.*)_phys.0/!p' file

OUTPUT:

#---------- SOLID: tank_phys.0
  DEF tank Shape {
abcdef
1234
#---------- SOLID: head_phys.0
  DEF head Shape { 
12345
gdfg

EXPLANATIONS:

/#---------- SOLID: (.*)_phys.0/{ #this block will be executed on each line respecting the regex /#---------- SOLID: (.*)_phys.0/
p; #print the line
s/#---------- SOLID: (.*)_phys.0/DEF \1/; #replace the line content using backreference to form DEF ...
N;#append next line Shape { to the pattern buffer
s/\n//;s/ {2,}/ /;s/^/  /p; #remove the new line, add/remove some spaces
b}; #jump to the end of the statements
/#---------- SOLID: (.*)_phys.0/!p #lines that does not respect the regex will just be printed

RavinderSingh13 · Answer 2 · 2018-03-27T05:49:48.543

0

Following simple awk may help you on same.

awk '/#---------- SOLID/{print;sub(/_.*/,"",$NF);val=$NF;getline;sub("Shape {","DEF " val " &")} 1'  Input_file

Output will be as follows.

[line 10] #---------- SOLID: tank_phys.0
[line 11]   DEF tank Shape {
...
[line 22] #---------- SOLID: head_phys.0
[line 23]   DEF head Shape {

edited Mar 27 '18 at 05:49

answered Mar 27 '18 at 04:07

RavinderSingh13

130,504
14
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I updated the input to make clear that the lines are not always same, so this awk solution does not work, thanks – user1301295 Mar 27 '18 at 04:26
@user1301295, your output is NOT looking consistent in your post shown why `{` is not there for first occurrence of `shape` ? If it is a typo then you would have tried my code I just tested it is working fine only, let me know on same? – RavinderSingh13 Mar 27 '18 at 04:28
Edit made, thanks. Coul you explain the code more, I'm only just learning sed and awk is new to me – user1301295 Mar 27 '18 at 04:44
@user1301295, sure edited the code as per your need, will add explanation too now in short time, cheers :) – RavinderSingh13 Mar 27 '18 at 05:50

score 0 · Answer 3 · answered Mar 27 '18 at 12:46

0

You can try this sed

sed -E '
  /SOLID/!b
  N
  s/(^.*SOLID: )([^_]*)(.*\n)([[:blank:]]*)(.*$)/\1\2\3\4DEF \2 \5/
' infile

answered Mar 27 '18 at 12:46

ctac_

2,413
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sed: remember capture in second expression

3 Answers3