grep

Arguments

haystack

A Row vector of character strings.

needle

A character string or a row vector of character strings . The string(s) to search in haystack.

row

vector of indices: row where a match has been found or an empty matrix if no match found.

which

vector of indices: index of needle string found or an empty matrix if no match found.

flag

Character ("r" for regular expression)

Description

Foreach entry of haystack, grep searches if at least a string in needle which matches a substring. The haystack entries index where at least a match has been found are returned in the row output argument. The optional which output argument gives the index of first string of needle found.

When using the third parameter flag="r", the needle is expected to be a regular expression string. In this case, grep uses the needle as a regular expression and compares it against haystack according to the regular express rules. See the regexp function for details about regular expressions.

Example #1

In the following example, we search one or two strings in a text, which is stored in the txt variable.

txt=['find matches of a string in a vector of strings'
     'search position of a character string in an other string'
     'Compare Strings'];

grep(txt,'strings')
grep(txt,['strings' 'Strings'])

[r,w]=grep(txt,['strings' 'Strings'])

Example #2

In the following example, we perform regexp searches.

str = ["hat";"cat";"hhat";"chat";"hcat";"ccchat";"at";"dog"]

grep(str,'/[hc]+at/','r')
grep(str,'/[hc]?at/','r')
grep(str,'/cat|dog/','r')

See Also

• strindex — search position of a character string in an other string.
• regexp — find a substring that matches the regular expression string