| | When using the programs in this book, such as grep and vi , you provide a regular expression that the program evaluates . The command will search for the pattern you supply. The pattern could be as simple as a string or it could wildcards. The wildcards used by many programs are called meta- characters . | Table 24-1 shows a list of meta-characters and the program(s) to which they apply. Only the programs covered in this book ( awk , grep , sed , and vi ) are shown in Table 24-1. These meta-characters may be used with other programs, such as ed and egrep , as well, which are not covered in the book. Table 24-1 describes the meta-characters and their use. Table 24-1. Meta-Characters and Programs to Which They Apply | Meta-Character | awk | grep | sed | vi | Use | | . | Yes | Yes | Yes | Yes | Match any single character. | | * | Yes | Yes | Yes | Yes | Match any number of the single character that precedes * . | | [ ... ] | Yes | Yes | Yes | Yes | Match any one of the characters in the set [ ... ] . | | $ | Yes | Yes | Yes | Yes | Matches the end of the line. | | ^ | Yes | Yes | Yes | Yes | Matches the beginning of the line. | | \ | Yes | Yes | Yes | Yes | Escape the special character that follows \ . | | \{ n,m \} | Yes | Yes | No | No | Match a range of occurrences of a single character between n and m . | | + | Yes | No | No | No | Match one or more occurrences of the preceding regular expression. | | ? | Yes | No | No | No | Match zero or one occurrence of the preceding regular expression. | | | Yes | No | No | No | The preceding or following regular expression can be matched. | | () | Yes | No | No | No | Groups regular expressions in a typical parenthetical fashion. | | \{ \} | No | No | No | Yes | Match a word's beginning or end. | You may want to refer to this table when regular expressions are used for one of the commands in the table. |