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Top Forums Shell Programming and Scripting Using sed and if multiple conditions Post 302909768 by Scrutinizer on Saturday 19th of July 2014 07:29:04 AM
Old 07-19-2014
Why would that break old scripts ? -a and -o will most likely remain supported by the implementations ...

Obsolescent means that is has become outdated and its usage is discouraged, for the reasons given and there is the intention to remove it from the standard..

Quote:
Q15. Does removal of obsolescent utility syntax mean that implementations supporting usages of head -5 file, tail -5 file, tail -l file are no longer allowed?

No, in general the intent of removing the obsolescent forms of the utility synopses was not to disallow them to be supported by implementations but to downgrade the status of their use in applications from conforming application using an obsolescent feature to non-conforming application. In general it is allowed for utilities to have extensions that violate the utility syntax guidelines so long as the forms defined in the standard that are required to follow the utility syntax guidelines do so. The cases cited fit the case. The Austin Group has more general cases under review at the present time.
POSIX.1 FAQ

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Quote:
Originally Posted by techy1
Strange. If i dont use the -o it just doesnt work. Its been a really long time since i had to use -o i forgot about that option
What version of ksh are you using on what OS? Even though older implementations are not POSIX compliant, they should support that syntax..

Last edited by Scrutinizer; 07-19-2014 at 08:41 AM..
 

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TAIL(1) 						    BSD General Commands Manual 						   TAIL(1)

NAME
tail -- display the last part of a file SYNOPSIS
tail [-F | -f | -r] [-q] [-b number | -c number | -n number] [file ...] DESCRIPTION
The tail utility displays the contents of file or, by default, its standard input, to the standard output. The display begins at a byte, line or 512-byte block location in the input. Numbers having a leading plus ('+') sign are relative to the beginning of the input, for example, ``-c +2'' starts the display at the second byte of the input. Numbers having a leading minus ('-') sign or no explicit sign are relative to the end of the input, for example, ``-n 2'' displays the last two lines of the input. The default start- ing location is ``-n 10'', or the last 10 lines of the input. The options are as follows: -b number The location is number 512-byte blocks. -c number The location is number bytes. -f The -f option causes tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the input. The -f option is ignored if the standard input is a pipe, but not if it is a FIFO. -F The -F option implies the -f option, but tail will also check to see if the file being followed has been renamed or rotated. The file is closed and reopened when tail detects that the filename being read from has a new inode number. If the file being followed does not (yet) exist or if it is removed, tail will keep looking and will display the file from the begin- ning if and when it is created. The -F option is the same as the -f option if reading from standard input rather than a file. -n number The location is number lines. -q Suppresses printing of headers when multiple files are being examined. -r The -r option causes the input to be displayed in reverse order, by line. Additionally, this option changes the meaning of the -b, -c and -n options. When the -r option is specified, these options specify the number of bytes, lines or 512-byte blocks to display, instead of the bytes, lines or blocks from the beginning or end of the input from which to begin the display. The default for the -r option is to display all of the input. If more than a single file is specified, each file is preceded by a header consisting of the string ``==> XXX <=='' where XXX is the name of the file unless -q flag is specified. EXIT STATUS
The tail utility exits 0 on success, and >0 if an error occurs. EXAMPLES
To display the last 500 lines of the file foo: $ tail -n 500 foo Keep /var/log/messages open, displaying to the standard output anything appended to the file: $ tail -f /var/log/messages SEE ALSO
cat(1), head(1), sed(1) STANDARDS
The tail utility is expected to be a superset of the IEEE Std 1003.2-1992 (``POSIX.2'') specification. In particular, the -F, -b and -r options are extensions to that standard. The historic command line syntax of tail is supported by this implementation. The only difference between this implementation and historic versions of tail, once the command line syntax translation has been done, is that the -b, -c and -n options modify the -r option, i.e., ``-r -c 4'' displays the last 4 characters of the last line of the input, while the historic tail (using the historic syntax ``-4cr'') would ignore the -c option and display the last 4 lines of the input. HISTORY
A tail command appeared in PWB UNIX. BSD
March 16, 2013 BSD
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