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--- grep_usage [2021/02/22 17:33] – raju
+++ grep_usage [2023/09/07 21:03] (current) – [repeat previous character N times] raju
@@ Line 1: / Line 1: @@
+==== dummy ====
+  * [[Remove lines with duplicate letters]]
+  * [[grep on find results]]
 ==== wordscapes ====
+tags | word scape, wordscape
 <code>
 % grep -i "^[slev][slev][slev][slev]s$" /usr/share/dict/american-english
 elves
 sells
+</code>
+Remove lines with duplicate letters
+<code>
+ % grep -Ei "^[hikers]{5}$" /usr/share/dict/american-english | grep -Eiv "(.).*\1"
+...
+shire
+shirk
+skier
+</code>
+compare this with
+<code>
+ % grep -Ei "^[hikers]{5}$" /usr/share/dict/american-english
+...
+shire
+shirk
+shirr
+sires
+sises
+skier
+skies
+</code>
+which also shows words where some letters are repeated twice.
+==== repeat previous character N times ====
+Use (character){N} and call grep with -E
+<code>
+ % grep -Ei "^[enrich]i([enrich]){2}e$" /usr/share/dict/american-english
+Circe
+niche
+niece
+</code>
+is equivalent to
+<code>
+ % grep -i "^[enrich]i[enrich][enrich]e$" /usr/share/dict/american-english
+Circe
+niche
+niece
+</code>
+Another example:
+<code>
+ % grep -Ei "^([dunes]){2}u([dunes]){2}d$" /usr/share/dict/american-english
+unused
+</code>
+==== print lines with less than a certain number of characters ====
+To print lines that contain less than N characters
+<code>
+grep -Ev ".{N}" data.txt
+</code>
+For example:
+To print lines that contain less then 6 characters
+<code>
+grep -Ev ".{6}" data.txt
+</code>
+You can also do
+<code>
+grep -v "......" data.txt
+</code>
+where the . is repeated N times. This is easier to type for small N.
+Sample run:
+<code>
+$ cat data.txt
+a
+ab
+abc
+abcd
+abcde
+abcdef
+abcdefg
+$ grep -v "......" data.txt
+a
+ab
+abc
+abcd
+abcde
+$ grep -Ev ".{6}" data.txt
+a
+ab
+abc
+abcd
+abcde
 </code>