Show all the file up to the match

Question

grep --before-context 5 shows 5 lines before the match.

I want to show everything before the match.
Doing grep --before-context 99999999 would work but it is not very... professional.

How to show all the file up to the match?

Answer 1

Sed is better for that.

Just do:

sed '/PATTERN/q' FILE

It works like this:

For each line, we look if it matches /PATTERN:

• if yes, we print it and quit
• otherwise, we print it

This is the most efficient solution, because as soon as it sees PATTERN, it quits. Without q, sed would continue to read the rest of the file, and do nothing with it. For big files it can make a difference.

This trick can also be used to emulate head:

sed 10q FILE

Answer 2

print up to and including the match:

awk '{print} /pattern/ {exit}' filename
sed '/pattern/q' filename

print up to BUT NOT including the match:

awk '/pattern/ {exit} {print}' filename
sed '/pattern/Q' filename

Answer 3

sed can replace most of grep's functionality.

sed -n '1,/<pattern>/ p' <file>

This means print from the first line until pattern is matched.

A couple of range examples

sed -n '/<pattern>/,$ p' <file> # from pattern to end of file
sed -n '/<pattern1>/,/<pattern2>/ p' <file> # from pattern1 to pattern2

Answer 4

For people who choose to remember only the basic tools in day to day work, and willing to accept less elegant and less efficient solutions:

head -n $(grep -n pattern filename | cut -d: -f1) filename

If this command is for a script then I will look for more elegant (and possibly efficient) solutions. If this is a one time command or a throw away script then I don't care.

Answer 5

Adding onto Mikel's answer above...

---

To print all lines up to, but not including, the first line in FILE containing PATTERN, try:

• sed '/.*PATTERN.*/{s///;q;}' FILE

This matches the entire line containing the pattern, replaces it with a blank line, then quits without processing the rest of the file.

---

Post-script:

The easiest/clearest way I could think of to prevent printing an extra newline at the end (without involving another tool), was to run sed again and delete the new final line:

sed '/.*PATTERN.*/{s///;q;}' FILE | sed '$d'

... and since we're now deleting that line anyway, our previous work is redundant and we can simplify to:

sed '/PATTERN/q' FILE | sed '$d'

Answer 6

The following pure GNU grep methods are not efficient.

Search for everything up to the first instance of string "foo" in file bar, using three greps:

grep -m 1 -B $(grep -n -m 1 foo bar | grep -o '^[0-9]*') foo bar

Matching up to the last instance of "foo":

grep -oPz "(?s)[^\n]*${s}.*?\n.*?foo.*?\n" bar

Note: details on the last grep can be found in: Regex (grep) for multi-line search needed.

Answer 7

You could also use one of the following

tac ./test | grep -B $(cat ./test | wc -l) -m 1 'pattern'|tac 

or

tac ./test |head -n $(tac ./test | grep -n 'pattern' | cut -d: -f1 | head -n 1)|tac

or

tac ./test |sed ':a;N;$!ba;s/\n/'"pattern"'/g' | sed 's/'"patternpattern"'/\n/g'|head -n 1|sed 's/'"pattern"'/\n/g'|tac

The first option is very similar to what the OP suggested only it makes sure ti show enough lines before context by counting the lines in the file

The second option searches the line number of the first match (you could change that as well by changing the inner 'head') and than uses head on that number

The last option replaces all new lines with the match and than replaces two adjacent matches with a new line. The output of this is a line for every block of text between two matches. After that it uses 'head' to choose the first line (mwaning the block of text until the first match) match and than retranslates each match to a new line. this option works only if the file is in the following format

pattern
texttexttext
texttexttext texttexttext
texttexttexttexttexttexttexttexttext
pattern
texttexttext
pattern 
texttexttext
texttexttexttexttexttexttexttexttext

and so forth

Answer 8

ruby -pe 'exit if /PATTERN/' file(s)

sed and alike is certainly preferable performance-wise. It can also be done as a Ruby one-liner with an order of magnitude performance penalty. This may be of interest if, in addition to stopping at a pattern, you want to do some processing that requires methods found in the standard Ruby library or a third-party Gem.

# Extract unique links from Markdown files
ruby -rcommonregex -ne \
  'puts $<.map{CommonRegex.get_links(_1)}.uniq.sort;
   exit if /PATTERN/' *.md

Aside from usefulness, its little known Ruby has adopted conventions found in awk or perl.