Let's say I have a variable

line="This is where we select from a table."

now I want to grep how many times does select occur in the sentence.

grep -ci "select" $line

I tried that, but it did not work. I also tried

grep -ci "select" "$line"

It still doesn't work. I get the following error.

grep: This is where we select from a table.: No such file or directory
up vote 65 down vote accepted

Have grep read on its standard input. There you go, using a pipe...

$ echo "$line" | grep select

... or a here string...

$ grep select <<< "$line"

Also, you might want to replace spaces by newlines before grepping :

$ echo "$line" | tr ' ' '\n' | grep select

... or you could ask grep to print the match only:

$ echo "$line" | grep -o select

This will allow you to get rid of the rest of the line when there's a match.

Edit: Oops, read a little too fast, thanks Marco. In order to count the occurences, just pipe any of these to wc(1) ;)

Another edit made after lzkata's comment, quoting $line when using echo.

  • 3
    Since the OP wants to count the number of occurrences of a string you can add a wc to complete the task: grep -o <string> <<< "$variable" | wc -l – Marco Oct 23 '14 at 15:39
  • 2
    Use echo "$line" to preserve existing newlines instead of creating ones with tr – Izkata Oct 23 '14 at 16:31
  • What is the availability of a Here String? Does it require Bash or another shell? – jww Jan 24 '16 at 20:43
  • According to Wikipedia, here strings are available in bash, ksh, and zsh (but I'm assuming there may be others). – John WH Smith Jan 24 '16 at 21:17
test=$line i=0
while case "$test" in (*select*)
test=${test#*select};;(*) ! :;;
esac; do i=$(($i+1)); done

You don't need to call grep for such a simple thing.

Or as a function:

occur() while case "$1" in (*"$2"*) set -- \
        "${1#*"$2"}" "$2" "${3:-0}" "$((${4:-0}+1))";;
        (*) return "$((${4:-0}<${3:-1}))";;esac
        do : "${_occur:+$((_occur=$4))}";done

It takes 2 or 3 args. Providing any more than that will skew its results. You can use it like:

_occur=0; occur ... . 2 && echo "count: $_occur"

...which prints the occurrence count of . in ... if it occurs at least 2 times. Like this:

count: 3

If $_occur is either empty or unset when it is invoked then it will affect no shell variables at all and return 1 if "$2" occurs in "$1" fewer than "$3" times. Or, if called with only two args, it will return 1 only if "$2" is not in "$1". Else it returns 0.

And so, in its simplest form, you can do:

occur '' . && echo yay || echo shite

...which prints...

shite

...but...

occur . . && echo yay || echo shite

...will print...

yay

You might also write it a little differently and omit the quotes around $2 in both the (*"$2"*) and "${1#*"$2"}" statement. If you do that then you can use shell globs for matches like sh[io]te for the match test.

  • 1
    +1: Faster, indeed. Works in bash and dash/sh (and probably a few others). – John WH Smith Oct 23 '14 at 16:22
  • @JohnWHSmith - the edit is better, but still just as portable. – mikeserv Oct 23 '14 at 17:55

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