The fgrep program does not expand any characters, but searches for exact matches of the character string you specify. Normally, both grep and fgrep will search the files you specify and produce a list, on standard output, of every line containing the text string matching the string or expression you specified. The grep command can expand special characters to find matches in much the way the shell expands special characters in file and directory names. Below is a simplified explanation of that expansion. The delimiters are required if the expression contains any blanks or special characters, and they can be used even if the expression does not contain such characters.
Any nonspecial character matches itself.
A period matches any character. If a set of characters is placed inside square brackets, each one is considered for matching in that position. You can use the hyphen within square brackets to denote an inclusive range. To do this, place the possible strings, one per line, in a file. Displays the line number with each line containing a match.