08-21-2008
Redirection related clarifications required...
There are two files named goody and good. Please look at their single line contents:-
$ cat goody
hi m goody
$ cat good
hi m good
1)
$ cat goody < good
hi m goody
When we give cat, a file to read from, standard input is ignored.
As such, the above operation will just display contents of goody.
2)
$ cat > goody < good
$ cat goody
hi m good
$ cat good
hi m good
What will be the output of the above command ? I think the command takes input from file good and then overwrites in goody and prints on terminal screen.
3) Whats the difference between a) cat goody >>= good and b) cat goody >> good
4) Whats the difference between a) cat goody >= good and b) cat goody > good
5) Whats the difference between cat < good and cat << good
Thanks a lot in advance.
Best Regards,
Marconi.
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LEARN ABOUT DEBIAN
plan9-cat
CAT(1) General Commands Manual CAT(1)
NAME
cat, read, nobs - catenate files
SYNOPSIS
cat [ file ... ]
read [ -m ] [ -n nline ] [ file ... ]
nobs [ file ... ]
DESCRIPTION
Cat reads each file in sequence and writes it on the standard output. Thus
cat file
prints a file and
cat file1 file2 >file3
concatenates the first two files and places the result on the third.
If no file is given, cat reads from the standard input. Output is buffered in blocks matching the input.
Read copies to standard output exactly one line from the named file, default standard input. It is useful in interactive rc(1) scripts.
The -m flag causes it to continue reading and writing multiple lines until end of file; -n causes it to read no more than nline lines.
Read always executes a single write for each line of input, which can be helpful when preparing input to programs that expect line-at-a-
time data. It never reads any more data from the input than it prints to the output.
Nobs copies the named files to standard output except that it removes all backspace characters and the characters that precede them. It is
useful to use as $PAGER with the Unix version of man(1) when run inside a win (see acme(1)) window.
SOURCE
/src/cmd/cat.c
/src/cmd/read.c
/bin/nobs
SEE ALSO
cp(1)
DIAGNOSTICS
Read exits with status eof on end of file or, in the -n case, if it doesn't read nlines lines.
BUGS
Beware of and which destroy input files before reading them.
CAT(1)