What grep command will include the current function name in its output?

Question

I run diff with the -p option so the output will include the name of the function where each change occurred. Is there an analogous option for

Answer 1

Here is an imperfect solution. It has the following flaws:

1. It requires a tool called ctags
2. Consequently, it works for C files, or any languages that ctags supports, but not beyond that
3. It displays all C function headers, no matter what. This is the biggest problem with my script, you might be able to find a way to overcome it.

I called my script `cgrep.sh', which has the following syntax:

cgrep.sh search-term files...

Cgrep.sh works by relying on ctags to produce a list of search patterns for function headers. We can then search for both the function headers and the search term. Without further ado, here is cgrep.sh:

#!/bin/sh

# Grep, which includes C function headers
# cgrep term files*

TERM=$1                             # Save the search term
shift

ctags "$@"                          # produces the tags file
sed -i.bak 's:^.*/^:^:;s:/$::' tags # Prepare the tags file for grep
                                    # Original contents is backed up to tags.bak
grep -f tags -e $TERM "$@"          # Grep both headers and search term
rm tags tags.bak                    # Clean up

Answer 2

Actually "grep -p" has been a fixture in AIX for the last two decades from what I can recall. It is out there, and it's just a matter of porting the behaviour over in fresh code.

It's crude, though, and may need help to know that blank lines within a function don't count.

Answer 3

I wrote a script to grep C files and show the C function names and signature along with the results. Based on ctags.

#!/bin/bash

#
# grep_c_code
#
# Grep C files and print the results along with the function name and signature.
# Requires: ctags, gawk, sed, bash, and you probably want grep too.
#
# Written by David Stav, December 19 2012.
#
# Released to the public domain.
#

if [ $# -lt 2 ]; then
    echo "Usage: $0 <grep_cmd> <files/dirs...>" >&2
    echo "" >&2
    echo "Example:" >&2
    echo "  $0 'grep --color=always -n -e \"PATTERN\"' file1 file2 dir1 dir2 | less -R" >&2
    exit 1
fi

GREP_CMD="$1"
shift

GAWK_SCRIPT="`
sed -n -e '/^##### START of gawk script #####$/,/^##### END of gawk script #####$/p' \"$0\" | \
sed -n -e '2,$ { $ D; p}'
`"

ctags -f - -R --sort=no -n --fields=+afikKmsSzt --extra=+fq "$@" | \
gawk "$GAWK_SCRIPT" "$GREP_CMD" | \
bash

exit 0

##### START of gawk script #####
function parse_line(a)
{
    a["tagname"] = $1;
    a["filename"] = $2;
    a["line_number"] = gensub(/^([0-9]+).*$/, "\\1", 1, $3);
    if (a["line_number"] == $3)
    {
        a["line_number"] = "0";
    }
    a["kind"] = gensub(/^.*\tkind:([^\t]+).*$/, "\\1", 1, $0);
    if (a["kind"] == $0)
    {
        a["kind"] = "unknown kind";
    }
    a["signature"] = gensub(/^.*\tsignature:(.*)$/, "\\1", 1, $0);
    if (a["signature"] == $0)
    {
        a["signature"] = "";
    }
}

function grep_section(a, next_line_number)
{
    printf("\n");
    printf("\n");
    printf("\n");
    printf("cat '%s' | \\\n", a["filename"]);
    printf("sed -n -e '%s,%sp' | \\\n", a["line_number"], next_line_number);
    printf("%s | \\\n", grep_cmd);
    printf("sed -e '1 i \\\n");
    printf("\\n\\n\\n--\\\n");
    printf("[%s:%s]\\\n", a["filename"], a["line_number"]);
    printf("<%s> %s%s\\\n", a["kind"], a["tagname"], a["signature"]);
    printf("'\n");
}

BEGIN \
{
    FS = "\t";
    grep_cmd = ARGV[1];
    ARGV[1] = ""
}

!/^!/ \
{
    parse_line(next_line);
    if (a["line_number"])
    {
        next_line_number = next_line["line_number"] - 1;
        grep_section(a, next_line_number);
        delete a;
    }
    for (key in next_line)
    {
        a[key] = next_line[key];
    }
}

END \
{
    if (a["line_number"])
    {
        next_line_number = "$";
        grep_section(a, next_line_number);
    }
}
##### END of gawk script #####

Enjoy. :)