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Comment: minor: added another awk example, to discourage ``grep foo | cut..''
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| This is really three different questions, so we'll break this answer into three parts. === foo AND bar on the same line === |
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| If you prefer, you can achieve this in one {{{sed}}} or {{{awk}}} statement. (The {{{awk}}} example is probably the most scalable.) | If you prefer, you can achieve this in one {{{sed}}} or {{{awk}}} statement: |
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| To match lines containing foo OR bar, {{{egrep}}} is the natural choice, but it can also be done with {{{sed}}}, {{{awk}}}, etc. | If you need to scale the awk solution to an arbitrary number of patterns, you can construct the awk command on the fly: {{{ # bash, ksh93 # Constructs awk "/$1/&&/$2/&&...." # Data to be matched should be on stdin. # Writes matching lines to stdout. multimatch() { (($# < 2)) && { echo "usage: multimatch pat1 pat2 [...]" >&2; return 1; } awk "/$1/$(printf "&&/%s/" "${@:2}")" } }}} === foo OR bar on the same line === There are lots of ways to match lines containing foo OR bar. `grep` can be given multiple patterns with `-e`: {{{ grep -e 'foo' -e 'bar' }}} Or you can construct one pattern with {{{egrep}}} (or `grep -E`): |
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| # some people prefer grep -E 'foo|bar' | grep -E 'foo|bar' }}} |
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| # This is another option, some people prefer: grep -e 'foo' -e 'bar' |
(You can't use the `|` union operator with plain `grep`. `|` is only available in [[RegularExpression|Extended Regular Expressions]].) |
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| # awk equivalent (eg if you want to extract fields) | It can also be done with {{{sed}}}, {{{awk}}}, etc. {{{ |
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| {{{egrep}}} is the oldest and most portable form of the {{{grep}}} command using Extended Regular Expressions (EREs). {{{-E}}} is a POSIX-required switch. | The `awk` approach has the advantage of letting you use `awk`'s other features on the matched lines, such as extracting only certain fields. To match lines that do not contain "foo" AND do not contain "bar": {{{ grep -E -v 'foo|bar' # some people prefer egrep -v 'foo|bar' }}} === foo AND bar in the same file, not necessarily on the same line === |
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| The double {{{grep -q}}} solution has the advantage of stopping each read whenever it finds a match; so if you have a huge file, but the matched words are both near the top, it will only read the first part of the file. Unfortunately, if the matches are near the bottom (worst case: very last line of the file), you may read the whole file two times. | |
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| Another approach is to read the file once, keeping track of what you've seen as you go along. There are several ways to do this in awk - the first example reads the whole file, and, after it reads the whole file, it checks if both were found: | Another approach is to read the file once, keeping track of what you've seen as you go along. In awk: |
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| awk '/foo/ { foo=1 } /bar/ { bar=1 } END { if (foo && bar) print "found both" }' | awk '/foo/{a=1} /bar/{b=1} a&&b{print "both found";exit} END{if (a&&b){ exit 0} else{exit 1}}' |
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| It reads the file one time, stopping when both patterns have been matched. No matter what happens, the END block is then executed, and the exit status is set accordingly. | |
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| The second, more efficient one avoids reading the whole file by checking if the other string was already matched, and, if so, exiting: {{{ awk 'function found() { print "Found both!"; exit } /foo/ { a=1; if (b) found() } /bar/ { b=1; if (a) found() }' }}} The double {{{grep -q}}} solution has the advantage of stopping each read whenever it finds a match; so if you have a huge file, but the matched words are both near the top, it will only read the first part of the file. The first awk solution reads the whole file one time, while the second one stops reading the file at the second match; if you want to do additional checking of the file contents, the awk solution can be adapted far more readily. |
If you want to do additional checking of the file's contents, this awk solution can be adapted quite easily. |
How can I grep for lines containing foo AND bar, foo OR bar? Or for files containing foo AND bar, possibly on separate lines?
This is really three different questions, so we'll break this answer into three parts.
foo AND bar on the same line
The easiest way to match lines that contain both foo AND bar is to use two grep commands:
grep foo | grep bar grep foo "$myfile" | grep bar # for those who need the hand-holding
It can also be done with one egrep, although (as you can probably guess) this doesn't really scale well to more than two patterns:
egrep 'foo.*bar|bar.*foo'
If you prefer, you can achieve this in one sed or awk statement:
sed -n '/foo/{/bar/p}'
awk '/foo/ && /bar/'If you need to scale the awk solution to an arbitrary number of patterns, you can construct the awk command on the fly:
# bash, ksh93
# Constructs awk "/$1/&&/$2/&&...."
# Data to be matched should be on stdin.
# Writes matching lines to stdout.
multimatch() {
(($# < 2)) && { echo "usage: multimatch pat1 pat2 [...]" >&2; return 1; }
awk "/$1/$(printf "&&/%s/" "${@:2}")"
}
foo OR bar on the same line
There are lots of ways to match lines containing foo OR bar. grep can be given multiple patterns with -e:
grep -e 'foo' -e 'bar'
Or you can construct one pattern with egrep (or grep -E):
egrep 'foo|bar' grep -E 'foo|bar'
(You can't use the | union operator with plain grep. | is only available in Extended Regular Expressions.)
It can also be done with sed, awk, etc.
awk '/foo|bar/'
The awk approach has the advantage of letting you use awk's other features on the matched lines, such as extracting only certain fields.
To match lines that do not contain "foo" AND do not contain "bar":
grep -E -v 'foo|bar' # some people prefer egrep -v 'foo|bar'
foo AND bar in the same file, not necessarily on the same line
If you want to match files (rather than lines) that contain both "foo" and "bar", there are several possible approaches. The simplest (although not necessarily the most efficient) is to read the file twice:
grep -q foo "$myfile" && grep -q bar "$myfile" && echo "Found both"
The double grep -q solution has the advantage of stopping each read whenever it finds a match; so if you have a huge file, but the matched words are both near the top, it will only read the first part of the file. Unfortunately, if the matches are near the bottom (worst case: very last line of the file), you may read the whole file two times.
Another approach is to read the file once, keeping track of what you've seen as you go along. In awk:
awk '/foo/{a=1} /bar/{b=1} a&&b{print "both found";exit} END{if (a&&b){ exit 0} else{exit 1}}'It reads the file one time, stopping when both patterns have been matched. No matter what happens, the END block is then executed, and the exit status is set accordingly.
If you want to do additional checking of the file's contents, this awk solution can be adapted quite easily.