How to find a position of a character?

Question

I need to identify the postion of a character in string.

Example, the string is RAMSITALSKHMAN|1223333.

grep -n '[^a-zA-Z0-9\$\~\%\#\^]'

How do I find the position of | in the given string?

Answer 1

You can use -b to get the byte offset, which is the same as the position for simple text (but not for UTF-8 or similar).

$ echo "RAMSITALSKHMAN|1223333" | grep -aob '|'
14:|

In the above, I use the -a switch to tell grep to use the input as text; necessary when operating on binary files, and the -o switch to only output the matching character(s).

If you only want the position, you can use grep to extract only the position:

$ echo "RAMSITALSKHMAN|1223333" | grep -aob '|' | grep -oE '[0-9]+'
14

If you get weird output, check to see if grep has colors enabled. You can disable colors by passing --colors=never to grep, or by prefixing the grep command with a \ (which will disable any aliases), e.g.:

$ echo "RAMSITALSKHMAN|1223333" | grep -aob '|' --color=never | \grep -oE '^[0-9]+'
14

For a string that returns multiple matches, pipe through head -n1 to get the first match.

Note that I use both in the above, and note that the latter will not work if grep is "aliased" through an executable (script or otherwise), only when using aliases.

Answer 2

If you're using the bash shell, you can use purely built-in operations without the need for spawning external processes such as grep or awk:

$ str="RAMSITALSKHMAN|1223333"
$ tmp="${str%%|*}"
$ if [ "$tmp" != "$str" ]; then
> echo ${#tmp}
> fi
14
$ 

This uses a parameter expansion to remove all occurrences of | follows by any string and save that in a temporary variable. It is then just a matter of measuring the length of the temporary variable to get the index of |.

Note the if is checking if the | exists at all in the original string. If it doesn't then the temporary variable will be the same as the orginal.

Note also this provides the zero-based index of | which is generally useful when indexing bash strings. However if you require the one-based index, then you can do this:

$ echo $((${#tmp}+1))
15
$ 

Answer 3

Try:

printf '%s\n' 'RAMSITALSKHMAN|1223333.' | grep -o . | grep -n '|'

output:

15:|

This will give you the position with index based-1.

Answer 4

You can use awk's index function to return the position in characters where the match occurs:

echo "RAMSITALSKHMAN|1223333"|awk 'END{print index($0,"|")}'
15

If you don't mind using the Perl's index function, this handles reporting zero, one or more occurrences of a character:

echo "|abc|xyz|123456|zzz|" | \
perl -nle '$pos=-1;while (($off=index($_,"|",$pos))>=0) {print $off;$pos=$off+1}'

For readability, only, the pipeline has been split across two lines.

As long as the target character is found, index returns a positive value based at zero (0). Hence, the string "abc|xyz|123456|zzz|" when parsed returns positions 0, 4, 8, 15 and 19.

Answer 5

We can also do it using "expr match" or "expr index"

expr match $string $substring where $substring is a RE.

echo `expr match "RAMSITALSKHMAN|1223333" '[A-Z]*.|'`

And above will give you the position because it returns the length of the substring matched.

But to be more specific for searching index :

mystring="RAMSITALSKHMAN|122333"
echo `expr index "$mystring" '|'`

Answer 6

Another awk command,

$ echo 'RAMSITALSKHMAN|1223333'| awk 'BEGIN{ FS = "" }{for(i=1;i<=NF;i++){if($i=="|"){print i;}}}'
15

By setting the Field separator as null string, awk turns individual character in the record as separate fields.

Answer 7

some alternatives include:

similar to Gnouc's answer, but with the shell:

echo 'RAMSITALSKHMAN|1223333' |
tr -c \| \\n | 
sh

sh: line 15: syntax error near unexpected token `|
sh: line 15: `|'

with sed and dc possibly spanning multiple lines:

echo 'RAMSITALSKHMAN|1223333' |
sed 's/[^|]/1+/g;s/|/p/;1i0 1+' |dc

15

with $IFS...

IFS=\|; set -f; set -- ${0+RAMSITALSKHMAN|1223333}; echo $((${#1}+1))

That will also tell you how many there are like...

echo $(($#-1))

Answer 8

Python answer

text='skfwlefk|3oeio|ajda'
print([idx for idx, char in enumerate(text) if char == '|'])
# prints '[8, 14]'