bash for with awk command inside - bash

Question

i have this piece of code of a bash script
for file in "$(ls | grep .*.c)"
do
cat $file |awk '/.*open/{print $0}'|awk -v nomeprog=$file 'BEGIN{FS="(";printf "the file e %s with the open call:", nameprog}//{ print $2}'
done
this give me this error :
*awk: cmd. line:1: file.c
awk: cmd. line:1: ^ syntax error
*i have this error when i have more of a file c into the folder , with just 1 file it works

Answer 1

Overall, you should probably follow Charles Duffy's recommendation to use more appropriate tools for the task. But I'd like to go over why the current script isn't working and how to fix it, as a learning exercise.
Also, two quick recommendations for shell script checking & troubleshooting: run your scripts through shellcheck.net to point out common mistakes, and when debugging put set -x before the problem section (and set +x after), so the shell will print out what it thinks is going on as the script runs.
The problem is due to how you're using the file variable. Let's look at what this does:
for file in "$(ls | grep .*.c)"
First, ls prints a list of files in the current directory, one per line. ls is really intended for interactive use, and its output can be ambiguous and hard to parse correctly; in a script, there are almost always better ways to get lists of filenames (and I'll show you one in a bit).
The output of ls is piped to grep .*.c, which is wrong in a number of ways. First, since that pattern contains a wildcard character ("*"), the shell will try to expand it into a list of matching filenames. If the directory contains any hidden (with a leading ".") .c files, it'll replace it with a list of those, and nothing is going to work at all right. Always quote the pattern argument to grep to prevent this.
But the pattern itself (".*.c") is also wrong; it searches for any number of arbitrary characters (".*"), followed by a single arbitrary character ("." -- this is in a regex, so "." is not treated literally), followed by a "c". And it searches for this anywhere in the line, so any filename that contains a "c" somewhere other than the first position will match. The pattern you want would be something like '[.]c$' (note that I wrapped it in single-quotes, so the shell won't try to treat $ as a variable reference like it would in double-quotes).
Then there's another problem, which is (part of) the problem you're actually experiencing: the output of that ls | grep is expanded in double-quotes. The double-quotes around it tell the shell not to do its usual word-split-and-wildcard-expand thing on the result. The common (but still wrong) thing to do here is to leave off the double-quotes, because word-splitting will probably break the list of filenames up into individual filenames, so you can iterate over them one-by-one. (Unless any filenames contain funny characters, in which case it can give weird results.) But with double-quotes it doesn't split them, it just treats the whole thing as one big item, so your loop runs once with file set to "src1.c\nsrc2.c\nsrc3.c" (where the \n's represent actual newlines).
This is the sort of trouble you can get into by parsing ls. Don't do it, just use a shell wildcard directly:
for file in *.c
This is much simpler, avoids all the confusion about regex pattern syntax vs wildcard pattern syntax, ambiguity in ls's output, etc. It's simple, clear, and it just works.
That's probably enough to get it to work for you, but there are a couple of other things you really should fix if you're doing something like this. First, you should double-quote variable references (i.e. use "$file" instead of just $file). This, is another part of the error you're getting; look at the second awk command:
awk -v nomeprog=$file 'BEGIN{FS="(";printf "the file e %s with the open call:", nameprog}//{ print $2}'
With file set to "src1.c\nsrc2.c\nsrc3.c", the shell will do its word-split-and-wildcard-expand thing on it, giving:
awk -v nomeprog=src1.c src2.c src3.c 'BEGIN{FS="(";printf "the file e %s with the open call:", nameprog}//{ print $2}'
awk will thus set its nomeprog variable to "src1.c", and then try to run "src2.c" as an awk command (on input files named "src3.c" and "BEGIN{FS=..."). "src2.c" is, of course, not a valid awk command, so you get syntax error.
This sort of confusion is typical of the chaos that can result from unquoted variable references. Double-quote your variable references.
The other thing, which is much less important, is that you have a useless use of cat. Anytime you have the pattern:
cat somefile | somecommand
(and it's just a single file, not several that need to be catenated together), you should just use:
somecommand <somefile
and in some cases like awk and grep, the command itself can take input filename(s) directly as arguments, so you can just use:
somecommand somefile
so in your case, rather than
cat "$file" | awk '/.*open/{print $0}' | awk -v nomeprog="$file" 'BEGIN{FS="(";printf "the file e %s with the open call:", nameprog}//{ print $2}'
I'd just use:
awk '/.*open/{print $0}' "$file" | awk -v nomeprog="$file" 'BEGIN{FS="(";printf "the file e %s with the open call:", nameprog}//{ print $2}'
(Although, as Charles Duffy pointed out, even that can be simplified quite a lot.)