I have a large file test.txt like this example:
foo
before ...
before some line
foo something interesting bar
after some lines
after ...
bar
How do I create a new file with just the lines before the first occurrence of the string "something interesting" with basic bash commands like sed or grep (not awk, I need this on an embedded device without awk)?
sed '/something interesting/,$d' < file > newfile
Which can be optimized to:
sed -n '/something interesting/q;p' < file > newfile
for sed to quit as soon as it finds the pattern.
Which with the GNU implementation of sed, as noted by @RakeshSharma, can be simplified to
sed '/something interesting/Q' < file > newfile
To truncate the file in-place, with ksh93 instead of bash, you could do:
printf '' <>; file >#'*something interesting*'
<>; is like the standard <> redirection operator (open in read+write) except that the file is truncated at the end if the command is successful.<#pattern seeks to the start of the next line matching the pattern.(note that it seems to work (with ksh93u+ at least) with printf '' on stdout but not with some other builtin commands like true, : or eval. Looks like a bug. Also it can't be the last command of a script (another bug)).
sed "/${VAR}/,$ d" - note the white space between $ and d.
sed -i '/something interesting/Q' 'file'
sedandgrepare notbashcommands; they are separate commands, which can be invoked from any shell you happen to be using.