How to delete only the last line of a ASCII text file using C?

问题

I have a text file. How do I go about deleting only the last line in the file using C?

Thanks! John.

回答1:

Plain ANSI C doesn't provide any standard way to decrease the size of a file - the only way to do this in standard C is to copy the entire file contents to a new file, except for the part you want to omit.

Alternatively, you can use OS-specific functions to truncate the file in-place. For example, POSIX provides the ftruncate() function, which shortens a file to a given length. You would search for the beginning of the last line, then truncate the file immediately before this (using lseek() to obtain the position).

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The easiest alternative of all, if you have GNU head, is just to use that:

head -n -1 < file.original > file.new

回答2:

You are correct with the approach. Sacn for newlines, remember the last one and then use truncate or ftruncate. see also How to truncate a file in C? .

hth

Mario

来源：https://stackoverflow.com/questions/4743561/how-to-delete-only-the-last-line-of-a-ascii-text-file-using-c