Include header in the 'grep' result

Question

Is there a way to combine 'head -1' and 'grep' command into one for all the files in a directory and redirect the output to an output file. I can do this using 'sed' but it seems that it is not as fast as grep.

sed -n '1p;/6330162/p' infile*.txt > outfile.txt 

Using grep I can do the following one file at a time:

head -1 infile1.txt;  grep -i '6330162' infile1.txt > outfile.txt 

However, I need to do it for all files in the directory. Inserting a wildcard is not helping as it is printing headers first and then the grep output.

Answer 1

The following means you only need type the command once (rather than using && and typing it twice), it's also quite simple to understand.

some-command | { head -1; grep some-stuff; } 

e.g.

ps -ef | { head -1; grep python; } 

UPDATE: This only seems to work for ps, sorry, but I guess this is usually what people want this for.

If you want this to work for an arbitrary command, it seems you must write a mini script, e.g.:

#!/bin/bash  first_line=true  while read -r line; do     if [ "${first_line}" = "true" ]; then         echo "$line"         first_line=false     fi     echo "$line" | grep $* done 

Which I've named hgrep.sh. Then you can use like this:

ps -ef | ./hgrep.sh -i chrome 

The nice thing about this approach is that we are using grep so all the flags work exactly the same.