\nAfter reading my post from yesterday<\/a>, I was in disbelief. I even tried the command there several more times – it works every time.<\/p>\n grep isn’t necessarily expected to support alternation – that is, the “or” operator, | (but grep -E does). Surprisingly, the system I experimented with yesterday indeed does support | with grep.<\/p>\n So, what are some differences between grep and grep -E (on this system, anyway)? Well, one is that grep needs escape sequences to specify specific multiples. For instance, the regex ^[a-zA-Z]{0,5} might mean 0 to 5 letters at the front of a string. I can do that with grep, this way:<\/p>\n grep “[a-zA-Z]\\{0,5\\}”<\/p>\n but with grep -E, this way:<\/p>\n grep -E “[a-zA-Z]{0,5}”<\/p>\n Relating to grep, the option -E means “enhanced” or “extended” functionality.<\/p>\n Source:<\/p>\n www.regular-expressions.info<\/a><\/p>\nJack of Oracle Tutoring by Jack and Diane,<\/a> Campbell River, BC.\n\n","protected":false},"excerpt":{"rendered":" Self-tutoring about Unix: the tutor continues about grep. After reading my post from yesterday, I was in disbelief. I even tried the command there several more times – it works every time. grep isn’t necessarily expected to support alternation – …<\/p>\n