Bash - tr(anslate)

tr(anslate) / Change caps to lower case
tr Man Page

cat sample.txt | tr [:upper:] [:lower:] > output.txt

delete ‘is’

cat sample.txt | tr -d ‘is’ > out.txt

Remove all the non-digit characters

echo “Phone number is 123-456-789” | tr -cd [:digit:] > output.txt
  • tr - Translate, squeeze, and/or delete characters from standard input
-c, -C, --complement
use the complement of SET1

-d, --delete
delete characters in SET1, do not translate

-s, --squeeze-repeats
replace each sequence of a repeated character that is listed in the last specified SET, with a single occurrence of that character

-t, --truncate-set1
first truncate SET1 to length of SET2

SETs are specified as strings of characters.  Most represent themselves.  

Interpreted sequences are:

       \NNN   character with octal value NNN (1 to 3 octal digits)

       \\     backslash

       \a     audible BEL

       \b     backspace

       \f     form feed

       \n     new line

       \r     return

       \t     horizontal tab

       \v     vertical tab

       CHAR1-CHAR2
              all characters from CHAR1 to CHAR2 in ascending order

       [CHAR*]
              in SET2, copies of CHAR until length of SET1

       [CHAR*REPEAT]
              REPEAT copies of CHAR, REPEAT octal if starting with 0

       [:alnum:]
              all letters and digits

       [:alpha:]
              all letters

       [:blank:]
              all horizontal whitespace

       [:cntrl:]
              all control characters

       [:digit:]
              all digits

       [:graph:]
              all printable characters, not including space

       [:lower:]
              all lower case letters

       [:print:]
              all printable characters, including space

       [:punct:]
              all punctuation characters

       [:space:]
              all horizontal or vertical whitespace

       [:upper:]
              all upper case letters

       [:xdigit:]
              all hexadecimal digits

       [=CHAR=]
              all characters which are equivalent to CHAR