I'm especially interested in being able to search file content for a condition.
1) There are times that I want to check a certain column in a certain row for content. An example of this would be checking a specific location in the file - specific line(s) and column(s) - for non-zero content; or checking it for a certain date; or that it has a number content greater, equal, or less than a certain value.
2) Checking a file that "contains" a certain string is limited when the string occurs more than once in the file, and I'm interested in a specific instance.
I may need to know not only that the string occurs once, but that it occurs "x" times. Or I may need to know that it appears at the bottom of the file.
When I want to identify a particular string that occurs towards the top of the file, in that case, it will generally have the same line number each time. However, if I want to check a particular line towards the bottom of the file, the line number will vary from day-to-day, but the relative position will always be the same (for example, it may always be the second to the last line in the file.)
Or I might be able to identify the string by context - the instance I'm interested in may always be immediately preceded or followed by another string on the line above or line below. (And it's important to know that they occurred together, since the other string may also have more than one instance in the file, and the relevant instance will be when they're together.)