How to list files and match first line in bash script?

Question

I would like to check for (only) python files for those which do not have the #!/usr/bin/env python in the first line. So, I write a bash script that does the following:

#!/bin/bash

#list all of python files

for file in `find . -name "*.py"`
do
        if [ `head -1 $file` != "#!/usr/bin/env python"] then;
                 echo "no match in file $file"
        else then;
                 echo "match!"
        fi
done

However, for some reason I cannot get the if statement correct! I've looked at many questions, but I cannot find one that succinctly describes the issue. Here is the error message:

./run_test.sh: line 9: syntax error near unexpected token `else'
./run_test.sh: line 9: `    else then;'

where am I going awry? Thank you.

correct syntax is : if [[ `head -1 $file` != "#!/usr/bin/env python" ]]; then. also delete the then; after else — amdixon
– amdixon, Commented Sep 5, 2015 at 2:05
Why is the double brackets ([[ and ]]) necessary? It doesn't work without them - I just checked. — makansij
– makansij, Commented Sep 5, 2015 at 3:37
Either you need to surround command in double quotes or use [[. If output of head -1 $file is more than one word or null, then it will break [ syntax. — Mahesh Kharvi
– Mahesh Kharvi, Commented Sep 5, 2015 at 5:09

Community · Accepted Answer · 2017-05-23 12:29:39Z

2

You can do something like

find . -type f -name '*.py' -exec \
  awk 'NR==1 && /#!\/usr\/bin\/env python/ \
  { print "Match in file " FILENAME; exit } \
  { print "No match in file " FILENAME; exit }' \
{} \;

If you are going to loop over it, don't use a for loop

#!/bin/bash
find . -type f -name '*.py' -print0 | while IFS= read -r -d $'\0' file; do
  if [[ $(head -n1 "$file") == "#!/usr/bin/env python" ]]; then
      echo "Match in file [$file]"
  else
      echo "No match in file [$file]"
  fi
done

edited May 23, 2017 at 12:29

CommunityBot

11 silver badge

answered Sep 5, 2015 at 3:07

Reinstate Monica Please

11.7k3 gold badges29 silver badges49 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Dimitris Fasarakis Hilliard · Accepted Answer · 2015-09-05 02:10:38Z

1

Things to notice:

The [] after your if statement needs correct spacing
The ';' (if you enter a new line is not necessary) goes after the if and not after the then

You added an extra then after the else.

#!/bin/bash

#list all of python files

for file in `find . -name "*.py"` 
do
     if [ `head -1 $file` != "#!/usr/bin/env python" ]; 
     then
         echo "no match in file $file"
     else 
         echo "match!"
     fi
done

answered Sep 5, 2015 at 2:10

Dimitris Fasarakis Hilliard

162k35 gold badges282 silver badges265 bronze badges

Comments

Sanjay Manohar · Accepted Answer · 2015-09-06 16:46:30Z

-1

can you use -exec option by any chance? I find it easier.

find . -name "*.py" -exec head -1 {} | grep -H '#!/usr/bin/env python' \;

You can control the output using grep options.

edit

Thanks to @chepner - To avoid the pipe being swallowed too early:

-exec sh -c "head -1 {} | grep -H '#!/usr/bin/env python'" \;

edited Sep 6, 2015 at 16:46

answered Sep 5, 2015 at 2:05

Sanjay Manohar

7,0564 gold badges37 silver badges61 bronze badges

7 Comments

lintuxvi Over a year ago

I like this since this most definitely seems like a one-off kind of task.

makansij Over a year ago

Yeah, I like this....what does the -H option do? I read the man page, but it doesn't make sense to me: ` -H Always print filename headers with output lines.`

Sanjay Manohar Over a year ago

oh, it should print the name of the file, before the matching text. I think -lHZ may actually be best for you, giving just zero-terminated filenames.

chepner Over a year ago

You can't have a pipeline in the argument to -exec.

chepner Over a year ago

-exec sh -c "head -1 {} | grep -H '#!/usr/bin/env python'" \;

|

Collectives™ on Stack Overflow

How to list files and match first line in bash script?

3 Answers 3

Comments

Comments

edit

7 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

edit

7 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related