【Mac】Regular Expressions for exact matching as words with grep and sed

• When we use grep or sed in our business, we often use word matching to search and replace.
• In this case, it is not uncommon that the exact match is not found.
• In this article, we will record the regular expression notation for doing so with a high probability of an exact match.

Result

• A description of the results is given first.
  • ※It is designed to work with BSD-style grep and sed on Mac.

# Data Example
$ cat data

10,30,50,100,150,250,300,500

# grep only 50 of the data examples
$ cat data | grep -o '[[:<:]]50[[:>:]]'

50

# Replace only 50 of the example data with "match".
$ cat data.txt | sed 's;[[:<:]]50[[:>:]];match;g'

10,30,match,100,150,250,300,500

Description

• The above example shows the process of search and replace for arbitrary data.
• The method used here is to enclose the word like [[:<:]]word[[:>:]].

grep

• In the first place, grep extracts not only words but also lines.
• To extract only words, use option and use grep -o word.
• However, in the above data example, there is a partial match as shown below, and four are extracted.

$ cat data | grep -o 50

50
50
50
50

• From these things, we use the [[:<:]]word[[:>:]] which has the following meanings.
  • Since it matches the beginning and end of a word, it does not recognize the character strings before and after.

sed

• The same is true for sed. If you replace it with the string as it is, it will be replaced 4 times.

$ cat data.txt | sed 's;50;match;g'

10,30,match,100,1match,2match,300,match0

• From these things, it is necessary to recognize it as a word like [[:<:]]word[[:>:]] like grep.

Conclusion

• From the above, I was reminded of further study of regular expressions, conscious of data duplication.

Link

• https://dev.mysql.com/doc/refman/5.6/en/regexp.html