grep the adb logcat & write the output to a text file

Question

I want to grep the adb logcat & write the output to a text file. If I just do

./adb logcat > std.txt 

it writes the entire log to the text file & If I do

./adb logcat | grep ABC 

it prints all lines containing ABC to my terminal. But now I wish to search for ABC & write only these lines to a text file.

./adb logcat | grep ABC > std.txt 

doesn't work. Plz help.

Answer 1

I think there is a problem with grep buffering. You can try something like this:

./adb logcat | grep --line-buffered ABC > std.txt 

It should be the same problem for chained grep.

EDIT: A similar question can be found here: Why no output is shown when using grep twice?.

Answer 2

Edit: This seems to work

 ./adb logcat |grep --line-buffered  ABC >a.txt 

---

I can explain you what is happening heres. Hope someone can derive a solution from that.If you run the following command in terminal

cat |grep "ABC" 

and start entering lines of text, you can see that grep immediately outputs any lines that contains.

 cat somefile.txt | grep "ABC"  

will print all lines that contains 'ABC' to the terminal, as expected.

But if you run

cat |grep ABC >a.txt 

and start entering text on the terminal, you can see that the file is not written until you enter an EOF character (Ctrl+ D) and make cat terminate.

But using --line-buffered gives output in the expected way

cat |grep --line-buffered  ABC >a.txt