Variable assignments specified with eval shell built-in Post: 302486408

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Top Forums UNIX for Advanced & Expert Users Variable assignments specified with eval shell built-in Post 302486408 by drl on Saturday 8th of January 2011 10:41:52 AM

01-08-2011

Registered User

Hi.

For this script:

Code:

#!/bin/bash --posix
#!/usr/bin/env dash
#!/usr/bin/env bash

# @(#) s1	Demonstrate IFS setting.

# Section 1, setup, pre-solution.
# Infrastructure details, environment, commands for forum posts. 
# Uncomment export command to test script as external user.
# export PATH="/usr/local/bin:/usr/bin:/bin"
set +o nounset
pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
# C=$HOME/bin/context && [ -f $C ] && . $C eval
version 2>&1 >/dev/null && version =o eval
set -o nounset
pe " posix setting: \"$(set -o | grep -i posix)\""
pe

# Section 2, solution.
pl " Results:"
pe " original: IFS is $(set | grep ^IFS | od -bc)"
var=$'a\nb c'
IFS=$'\n' eval '
pe " before loop: IFS is $(set | grep ^IFS | od -bc)"
for i in $var; do
  echo "$i"
done
'
pe " after loop:  IFS is $(set | grep ^IFS | od -bc)"

exit 0

The setting stays the same:

Code:

% ./s1
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 (lenny) 
eval - is a shell builtin [bash]
 posix setting: "posix          	on"


-----
 Results:
 original: IFS is 0000000 111 106 123 075 047 040 011 012
          I   F   S   =   '      \t  \n
0000010
 before loop: IFS is 0000000 111 106 123 075 047 012
          I   F   S   =   '  \n
0000006
a
b c
 after loop:  IFS is 0000000 111 106 123 075 047 012
          I   F   S   =   '  \n
0000006

I think this is what you expected.

The dash and plain bash did not keep the before-loop setting ... cheers, drl

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LEARN ABOUT SUNOS

endusershell

getusershell(3C)					   Standard C Library Functions 					  getusershell(3C)

NAME

       getusershell, setusershell, endusershell - get legal user shells

SYNOPSIS

       #include <unistd.h>

       char *getusershell(void);

       void setusershell(void);

       void endusershell(void);

DESCRIPTION

       The  getusershell()  function  returns  a  pointer  to  a  legal  user  shell  as defined by the system manager in the file /etc/shells. If
       /etc/shells does not exist, the following locations of the standard system shells are used in its place:

       /bin/bash		  /bin/csh
       /bin/jsh 		  /bin/ksh
       /bin/pfcsh		  /bin/pfksh
       /bin/pfsh		  /bin/sh
       /bin/tcsh		  /bin/zsh
       /sbin/jsh		  /sbin/pfsh
       /sbin/sh 		  /usr/bin/bash
       /usr/bin/csh		  /usr/bin/jsh
       /usr/bin/ksh		  /usr/bin/pfcsh
       /usr/bin/pfksh		  /usr/bin/pfsh
       /usr/bin/sh		  /usr/bin/tcsh
       /usr/bin/zsh		  /usr/xpg4/bin/sh

       The getusershell() function opens the file /etc/shells, if it exists, and returns the next entry in the list of shells.

       The setusershell() function rewinds the file or the list.

       The endusershell() function closes the file, frees any memory used by getusershell() and setusershell(), and rewinds the file /etc/shells.

RETURN VALUES

       The getusershell() function returns a null pointer on EOF.

BUGS

       All information is contained in memory that may be freed with a call to endusershell(), so it must be copied if it is to be saved.

SunOS 5.10							    30 Aug 2004 						  getusershell(3C)

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