Hi! Line numbers from Issue 8 (C243).
116577 DESCRIPTION 116578 The tail utility shall copy its input file to the standard output beginning at a designated place. 116579 Copying shall begin at the point in the file indicated by the −c number or −n number options. The 116580 option-argument number shall be counted in units of lines or bytes, according to the options −n 116581 and −c. Both line and byte counts start from 1. (So tail is defined in terms of "seek to start of data, dump to end".) 116584 OPTIONS 116588 −c number The application shall ensure that the number option-argument is a decimal integer, 116589 optionally including a sign. The sign shall affect the location in the file, measured 116590 in bytes, to begin the copying: 116591 Sign Copying Starts 116592 + Relative to the beginning of the file. 116593 − Relative to the end of the file. 116594 none Relative to the end of the file. 116595 The application shall ensure that if the sign of the number option-argument is '+', 116596 the number option-argument is a non-zero decimal integer. 116597 The origin for counting shall be 1; that is, −c +1 represents the first byte of the file, 116598 −c −1 the last. 116605 −n number If −r is not specified, this option shall be equivalent to −c number, except the 116606 starting location in the file shall be measured in lines instead of bytes. The origin 116607 for counting shall be 1; that is, −n +1 represents the first line of the file, −n −1 the 116608 last. (So -n 2 and -n -2 mean "start of data is start of line before the last".) Thus (and knowing that a line is 1800 A sequence of zero or more non-<newline> characters plus a terminating <newline> character. ), given $ printf 'abc\ndef\nghi\njkl' > l We can thus analyse it into lines: 1. abc\n 2. def\n 3. ghi\n (also some garbage) Thus the following must hold: $ tail -n 2 l; echo def ghi jkl since tail sought to start of the line before the last (2) and dumped 'til end. But this is both obviously wrong and also not how any implementation behaves. GNU coreutils and FreeBSD and NetBSD and the illumos gate all do the expected thing of $ tail -n 2 l; echo ghi jkl Maybe add something to the effect of ", except the starting location in the file shall be measured in lines or partial lines instead of bytes."? Best, наб
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