Amazon Interview Question for

屌丝

Shell command, there is a log file, you want all the "error" inside the line to find out into another file inside,
What instruction,

非丽丝

grep "Error" app.log>>AppError.log

妮可

grep -rnw '/path/to/somewhere/' -e 'pattern'
-r or -R is recursive,
-n is line number, and
-w stands for match the whole word.
-l (lower-case L) can be added to just give the file name of matching files.
Along with these, --exclude, --include, --exclude-dir or --include-dir flags could be used for efficient searching:

This will only search through those files which have .c or .h extensions:
grep --include=\*.{c,h} -rnw '/path/to/somewhere/' -e "pattern"