Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Help in explaining this echo conundrum.
Operating Systems OS X (Apple) Help in explaining this echo conundrum. Post 302993798 by wisecracker on Tuesday 14th of March 2017 01:41:35 PM
Old 03-14-2017
Help in explaining this echo conundrum.
OSX 10.12.3, default bash terminal.
Consider this code and note it is calling 'sh' inside the code...
Code:
#!/bin/sh
echo '1\n2\n2\n3\n5' > /tmp/text
hexdump -C /tmp/text
/bin/echo '1\n2\n3\n4\n5' > /tmp/text
hexdump -C /tmp/text

Now view the interactive mode below, note the underlying shell is bash:-
Code:
Last login: Tue Mar 14 17:12:45 on ttys001
AMIGA:barrywalker~> # Use sh first...
AMIGA:barrywalker~> sh
AMIGA:barrywalker~> cd Desktop/Code/Shell
AMIGA:barrywalker~/Desktop/Code/Shell> echo '1\n2\n3\n4\n5' > /tmp/text
AMIGA:barrywalker~/Desktop/Code/Shell> hexdump -C /tmp/text
00000000  31 0a 32 0a 33 0a 34 0a  35 0a                    |1.2.3.4.5.|
0000000a
AMIGA:barrywalker~/Desktop/Code/Shell> /bin/echo '1\n2\n3\n4\n5' > /tmp/text
AMIGA:barrywalker~/Desktop/Code/Shell> hexdump -C /tmp/text
00000000  31 5c 6e 32 5c 6e 33 5c  6e 34 5c 6e 35 0a        |1\n2\n3\n4\n5.|
0000000e
AMIGA:barrywalker~/Desktop/Code/Shell> ./echo_test.sh
00000000  31 0a 32 0a 32 0a 33 0a  35 0a                    |1.2.2.3.5.|
0000000a
00000000  31 5c 6e 32 5c 6e 33 5c  6e 34 5c 6e 35 0a        |1\n2\n3\n4\n5.|
0000000e
AMIGA:barrywalker~/Desktop/Code/Shell> # Now exit sh...
AMIGA:barrywalker~/Desktop/Code/Shell> exit
exit
AMIGA:barrywalker~> bash -version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin16)
Copyright (C) 2007 Free Software Foundation, Inc.
AMIGA:barrywalker~> cd Desktop/Code/Shell
AMIGA:barrywalker~/Desktop/Code/Shell> echo '1\n2\n3\n4\n5' > /tmp/text
AMIGA:barrywalker~/Desktop/Code/Shell> hexdump -C /tmp/text
00000000  31 5c 6e 32 5c 6e 33 5c  6e 34 5c 6e 35 0a        |1\n2\n3\n4\n5.|
0000000e
AMIGA:barrywalker~/Desktop/Code/Shell> /bin/echo '1\n2\n3\n4\n5' > /tmp/text
AMIGA:barrywalker~/Desktop/Code/Shell> hexdump -C /tmp/text
00000000  31 5c 6e 32 5c 6e 33 5c  6e 34 5c 6e 35 0a        |1\n2\n3\n4\n5.|
0000000e
AMIGA:barrywalker~/Desktop/Code/Shell> ./echo_test.sh
00000000  31 0a 32 0a 32 0a 33 0a  35 0a                    |1.2.2.3.5.|
0000000a
00000000  31 5c 6e 32 5c 6e 33 5c  6e 34 5c 6e 35 0a        |1\n2\n3\n4\n5.|
0000000e
AMIGA:barrywalker~/Desktop/Code/Shell> _

1) Why does the 'bash' interactive mode give a different result to the 'sh' mode as 'sh' is merely a subset of 'bash'?
2) Why does echo in 'sh' translate '\n' to newlines in single quotes?
I thought single quotes were to give a raw string of characters, irrespective?
(Is this an Apple OSX thing?)
The 'sh' version is the same as the 'bash' version but are NOT identical files.

TIA...
 

8 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

explaining awk

i am new to awk scripting. i couldn't figure out how this awk script works can anyone explain? #!/bin/awk -f { for( x=1; x<=NF; ++x) { if( x == 3 ) { continue } print x, $x } } thank you and regards (1 Reply)
Discussion started by: phone_book
1 Replies

2. UNIX for Dummies Questions & Answers

Need help explaining how to use a VPN on a UNIX server with a Mac OS

I have gotten a gig to teach someone how to use a VPN client for a UNIX server on a MAC os. The problem is I have never used UNIX, dont mess with VPN's (my dad has a VPN that I have used a couple of times). I'm currently taking a crash course on UNIX but I was wondering if anyone could help me with... (0 Replies)
Discussion started by: psycopuppy
0 Replies

3. UNIX for Dummies Questions & Answers

Explaining some lines from files : .login and .cshrc

Hello, can anyone explain me please what do those lines do ? From file .login 1) set history=40 2) setenv MACH `uname -s` 3) source /etc/login 4) source ~/$MACH/.login From file .cshrc 1) if ( ! $?prompt) exit 0 (5 Replies)
Discussion started by: bbqtoss
5 Replies

4. UNIX for Dummies Questions & Answers

umask conundrum

Hi All, i was reading up on a umask question on this forum and have a question on this. the umask value on my home PC running on cygwin is 022. when i create a dir it defaults to permission 755, when i create a file it defaults to 644. Now it starts at 777 for dirs and 666 for files and... (1 Reply)
Discussion started by: Irishboy24
1 Replies

5. Shell Programming and Scripting

Conundrum - Flexible way to strip extension

Hi, First post here. I have something that may prove to be difficult. I have the following files: Example1.0.0.tar.gz Example2.tar Example3.zip Example4.0.0.0.0.0.bzip2 I need to remove the file extensions and store as a variable so they look like this: Example1.0.0 Example2... (3 Replies)
Discussion started by: Spadez
3 Replies

6. Shell Programming and Scripting

sudo scripts conundrum

hello; Got a problem running monitoring scripts using sudo ssh.. Mgmt decided to take away root sudoers access.. so most of the scripts ran as: sudo ssh $BOX ... Now I need to run them as: echo $my_pw | sudo -S -l my_user_id $BOX ... I tried this but not working.. Any wisdom/tricks... (3 Replies)
Discussion started by: delphys
3 Replies

7. Shell Programming and Scripting

Help to explaining a command in run dot tcl

Hi, I'm running a rdt (run dot tcl) command, and come accross this line: alias abc 'set ARGS =(\!*); source home123/abc/$ARGS/setup' What does the command exactly do? Please help. (6 Replies)
Discussion started by: mar85
6 Replies

8. IP Networking

iptables conundrum

Ok, if youre reading this prepare yourself.(debian based os) so im trying to do this routing with ip tables, i need to forward/SNAT traffic from 192.168.111.1 to 10.10.10.250, the 192.x.x.x ips are being shoved into a honeyd like program called inetsim so its offline, 10.10.10.125 is connected... (3 Replies)
Discussion started by: Shocco
3 Replies

LEARN ABOUT OSX

cpanplus::shell

CPANPLUS::Shell(3pm)					 Perl Programmers Reference Guide				      CPANPLUS::Shell(3pm)

NAME

       CPANPLUS::Shell - base class for CPANPLUS shells

SYNOPSIS

	   use CPANPLUS::Shell; 	    # load the shell indicated by your
					    # config -- defaults to
					    # CPANPLUS::Shell::Default

	   use CPANPLUS::Shell qw[Classic]  # load CPANPLUS::Shell::Classic;

	   my $ui      = CPANPLUS::Shell->new();
	   my $name    = $ui->which;	    # Find out what shell you loaded

	   $ui->shell;			    # run the ui shell

DESCRIPTION

       This module is the generic loading (and base class) for all "CPANPLUS" shells. Through this module you can load any installed "CPANPLUS"
       shell.

       Just about all the functionality is provided by the shell that you have loaded, and not by this class (which merely functions as a generic
       loading class), so please consult the documentation of your shell of choice.

BUG REPORTS

       Please report bugs or other issues to <bug-cpanplus@rt.cpan.org<gt>.

AUTHOR

       This module by Jos Boumans <kane@cpan.org>.

COPYRIGHT

       The CPAN++ interface (of which this module is a part of) is copyright (c) 2001 - 2007, Jos Boumans <kane@cpan.org>. All rights reserved.

       This library is free software; you may redistribute and/or modify it under the same terms as Perl itself.

SEE ALSO

       CPANPLUS::Shell::Default, CPANPLUS::Shell::Classic, cpanp

perl v5.16.2							    2012-10-11						      CPANPLUS::Shell(3pm)
All times are GMT -4. The time now is 02:04 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy