Combining find grep and tail

findgreptail

I am trying to find all files that start with a certain name, then go through each file to find lines that contains a string, then only print out the last line of each file that contain the string. Step by step, I first find all files in my directory that start with "A123"

find . -name 'A123*'

then get each line in the file that contains "Trial"

find . -name 'A123*' -exec grep 'Trial' {} \;

and then from here I only want to print the last line,

find . -name 'A123*' -exec grep 'Trial' {} | tail -1 \;

however, this last command does not work. How do I fix this to get what I am trying to get?

Best Answer

| is a shell operator, so the whole output of find will be passed to tail. You need to run only a single command in exec by grouping all the commands to run and pass to sh or bash (or any shells you prefer)

find . -name 'A123*' -exec bash -c 'grep Trial "$1" | tail -1' grep {} \;

Or you can just use some other single commands for getting the last match from How to grep the last occurrence of a line pattern

If you can make sure that you files contain no special characters like #$/\`&*~-... in their names you can use this

find . -name 'A123*' -exec bash -c "grep 'Trial' {} | tail -1" \;

But please be aware that strange things may happen there when there are unexpected names you didn't know. For more information read Is it possible to use find -exec sh -c safely?

Related Solutions

Bash – Efficient way to search string within file find and grep

The fastest I can come up with is to use xargs to share the load:

find . -type f -print0  | xargs -0 grep -Fil "mypattern"

Running some benchmarks on a directory containing 3631 files:

$ time find . -type f -exec grep -l -i "mystring" {} 2>/dev/null \;

real    0m15.012s
user    0m4.876s
sys     0m1.876s

$ time find . -type f -exec grep -Fli "mystring" {} 2>/dev/null \;

real    0m13.982s
user    0m4.328s
sys     0m1.592s


$ time find . -type f -print0  | xargs -0 grep -Fil "mystring" >/dev/null 

real    0m3.565s
user    0m3.508s
sys     0m0.052s

Your other options would be to streamline either by limiting the file list using find:

   -executable
          Matches files which are executable and  direc‐
          tories  which  are  searchable (in a file name
          resolution sense).  
   -writable
          Matches files which are writable.             

   -mtime n
          File's  data was last modified n*24 hours ago.
          See the comments for -atime to understand  how
          rounding  affects  the  interpretation of file
          modification times.
   -group gname
          File  belongs to group gname (numeric group ID
          allowed).
   -perm /mode
          Any  of  the  permission bits mode are set for
          the file.  Symbolic modes are accepted in this
          form.  You must specify `u', `g' or `o' if you
          use a symbolic mode. 
   -size n[cwbkMG]  <-- you can set a minimum or maximum size
          File uses n units  of  space.

Or by tweaking grep:

You are already using grep's -l option which cause the file name to be printed and, more importantly, stops at the first match:

   -l, --files-with-matches
       Suppress normal output; instead print the name of each input file  from
       which  output would normally have been printed.  The scanning will stop
       on the first match.  (-l is specified by POSIX.)

The only other thing I can think of to speed things up would be to make sure your pattern is not interpreted as a regex (as suggested by @suspectus) by using the -F option.

Linux – Filter tail command through multiple grep commands to separate files

It might be easier if you use more than one line to do this. You could write a bash script:

#!/bin/bash

tail -f test.log | while read line; do
    if echo "$line" | grep -q "Error"; then
        echo "$line" >> error.log
    elif echo "$line" | grep -q "Warning"; then
        echo "$line" >> warning.log
    # The following is in case you want to print out lines that do not match 
    else
        echo "$line"
    fi
done

Best Answer

Related Solutions

Bash – Efficient way to search string within file find and grep

Linux – Filter tail command through multiple grep commands to separate files

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