Question

I want to check if a single char is in a C string. The character is the '|'
used for pipelines in Linux (Actually, I also want to check for '<', '>', '>>', '&').

In Java I can do this:

String.indexOf()

But how can I do this in C, without looping through the whole string (a char* string)?

Answer 1

If you need to search for a character you can use the strchr function, like this:

char* pPosition = strchr(pText, '|');

pPosition will be NULL if the given character has not been found. For example:

puts(strchr("field1|field2", '|'));

Will output: “|field2”. Note that strchr will perform a forward search, to search backward you can use the strrchr. Now imagine (just to provide an example) that you have a string like this: “variable:value|condition”. You can extract the value field with:

char* pValue = strrchr(strchr(pExpression, '|'), ':') + 1;

If what you want is the index of the character inside the string take a look to this post here on SO. You may need something like IndexOfAny() too, here another post on SO that uses strnspn for this.

Instead if you’re looking for a string you can use the strstr function, like this:

char* pPosition = strstr(pText, "text to find");