awk command not getting executed in shell script

Shell Programming and Scripting
1

I am able to execute awk command from shell prompt. but the same command is not getting executed when written and run in a bash script

the command from bash cmd prompt.

awk '/world/{for (i=2; i<NF; i++) printf $i " "; print $NF}1' myfile >tmp$$ ; mv tmp$$ myfile

file:
#  hello world my friend
# this is a beautiful place
$ mary had a little lamb
# jhony jhony yes papa
 
OP
hello world my friend
# this is a beautiful place
$ mary had a little lamb
# jhony jhony yes papa

But the same thing on trying with a bash script, no output is observed
script

#!/bin/bash
#!/usr/bin/awk 
NAME="world"
awk '/$NAME/{for (i=2; i<NF; i++) printf $i " "; print $NF}1' myfile >tmp$$ ; mv tmp$$ myfile
2

There's two reasons that construct doesn't work - neither within nor without a script:

  • within single quotes shell expansion is not performed - $NAME is taken literally.
  • awk interprets anything between / as a regex constant - again, $NAME will be taken literally.

Use the -v option to awk to hand over parameters, and use the match function in lieu of the /... /

On top, only the shebang in the first line will be interpreted.

3

Hello Ashima,

In awk value of variables dosn't work like shell ones. Could you please try following and let me know if this helps you.

#!/bin/bash
NAME="world"
awk -vname=$NAME  '{if($0 ~ /name/){for (i=2; i<NF; i++) printf $i " "; print $NF}}1' myfile >tmp$$ ; mv tmp$$ myfile

Let me know if you have any queries.

Thanks,
R. Singh

4

no, this won't work either for the reasons RudiC explained above.

#!/bin/bash
NAME="world"
awk -vname=$NAME  '$0 ~ name{for (i=2; i<NF; i++) printf $i " "; print $NF}1' myfile >tmp$$ ; mv tmp$$ myfile
1 Like
5 
awk '/world/{for (i=2; i<NF; i++) printf $i " "; print $NF}1' myfile >tmp$$ ; mv tmp$$ myfile

I am afraid that the above command will never produce what you said, but rather the following:

hello world my friend
#  hello world my friend
# this is a beautiful place
$ mary had a little lamb
# jhony jhony yes papa

If your intention is to remove the comment and the spaces in front of any sentence that has the word `world', perhaps sed would be a bit more suitable for it.

#!/bin/bash
NAME="world"
sed "/$NAME/ s/^#[[:blank:]]*//" myfile >tmp$$
mv tmp$$ myfile