exec in this form is for redirecting the file descriptors of the process.
Think of it this way; if you always want to do "myscript 2>/tmp/fnord 1>&2" then you can say this inside myscript, right at the beginning:
Then the redirections are no longer needed at the prompt when you run myscript.
So in your example, the script's input file descriptor (what every command will be reading from if not given a file argument -- read, cat, grep, you name it) from that point on is /dev/console, output from all commands will go to /dev/console (unless separately redirected, of course), and errors will go to the same (2>&1 means send standard error where-ever standard output is).
Sir,
I using the following commands in a file (part of a bigger script):
#!/bin/bash
cd /opt/oracle/bin
ls -lt | tail -1 | awk '{print $6}' >> /tmp/ramb.out
If I run this from the command prompt the result is:
2007-05-16
if I run it as a cron job then... (5 Replies)
Hi ,
I have a piece of code ...wherein I need to assign the following ...
1) A command line argument to a variable
e.g origCount=ARGV
2) A unix command to a variable
e.g result=`wc -l testFile.txt`
in my awk shell script
When I do this :
print "origCount" origCount --> I get the... (0 Replies)
AIX:Command to get netaddress/subnet address command in IPv4/IP6
Can anybody help us with a command to retrieve netaddress/subnet address command in IPv4/IP6 on aix machine.
net/subnet address is in the format 172.16.212.0(signifies all 255 machines in an IPv4 network) (2 Replies)
Hi everyone,
when executing this command in unix:
echo "WM7 Fatal Alerts:", $(cat query1.txt) > a.csvIt works fine, but running this command in a shell script gives an error saying that there's a syntax error.
here is content of my script:
tdbsrvr$ vi hc.sh
"hc.sh" 22 lines, 509... (4 Replies)
Hi,
Well my title isn't very clear I think. So to understand my goal:
I have a script "test1"
#!/bin/bash
xvkbd -text blabla
with xbindkeys, I bind F5 key in order it runs my test1 script
So when I press F5, test1 runs.
I'm under Emacs/Vi and I press F5 in order to have "blabla" be... (0 Replies)
HI Guys,
I hope you are well. I am trying to write a script that gets executed every time i open a shell (cshell). I have two questions about that
1) I need to enter these commands
$ echo $DISPLAY
$ setenv $DISPLAY output_of_echo_$display_command
How can i write a... (2 Replies)
I am working with a sh script on a solaris 9 zone (sol 10 host) that grabs information to build the configuration command line. the variables Build64, SSLopt, CONFIGopt, and CC are populated in the script. the script includes
CC=`which gcc`
CONFIGopt=' --prefix=/ --exec-prefix=/usr... (8 Replies)
below is the output xml string from some other command and i will be parsing it using awk
cat /tmp/alerts.xml
<Alert id="10102" name="APP-DS-ds_ha-140018-componentFailure-S" alertDefinitionId="13982" resourceId="11427" ctime="1359453507621" fixed="false" reason="If Event/Log Level(ANY) and... (2 Replies)
exec(): 0509-036 Cannot load program /usr/opt/freeware/bin/rpm because of the following errors:
0509-022 Cannot load module /opt/freeware/lib/libintl.a(libintl.so.1).
0509-150 Dependent module /opt/freeware/lib/libiconv.a(shr4.o) could not be loaded.
0509-152 Member... (4 Replies)
Hello Forum,
I'm making very good progress on my report thanks to the very helpful people on this forum. I've been able to successfully create my report for my Red Hat servers. But I do have a few ubuntu servers in the mix and I'd like to capture some data from them when an ssh connection is... (8 Replies)
Discussion started by: greavette
8 Replies
LEARN ABOUT LINUX
pivot_root
PIVOT_ROOT(8) Maintenance Commands PIVOT_ROOT(8)NAME
pivot_root - change the root file system
SYNOPSIS
pivot_root new_root put_old
DESCRIPTION
pivot_root moves the root file system of the current process to the directory put_old and makes new_root the new root file system. Since
pivot_root(8) simply calls pivot_root(2), we refer to the man page of the latter for further details.
Note that, depending on the implementation of pivot_root, root and cwd of the caller may or may not change. The following is a sequence for
invoking pivot_root that works in either case, assuming that pivot_root and chroot are in the current PATH:
cd new_root
pivot_root . put_old
exec chroot . command
Note that chroot must be available under the old root and under the new root, because pivot_root may or may not have implicitly changed the
root directory of the shell.
Note that exec chroot changes the running executable, which is necessary if the old root directory should be unmounted afterwards. Also
note that standard input, output, and error may still point to a device on the old root file system, keeping it busy. They can easily be
changed when invoking chroot (see below; note the absence of leading slashes to make it work whether pivot_root has changed the shell's
root or not).
EXAMPLES
Change the root file system to /dev/hda1 from an interactive shell:
mount /dev/hda1 /new-root
cd /new-root
pivot_root . old-root
exec chroot . sh <dev/console >dev/console 2>&1
umount /old-root
Mount the new root file system over NFS from 10.0.0.1:/my_root and run init:
ifconfig lo 127.0.0.1 up # for portmap
# configure Ethernet or such
portmap # for lockd (implicitly started by mount)
mount -o ro 10.0.0.1:/my_root /mnt
killall portmap # portmap keeps old root busy
cd /mnt
pivot_root . old_root
exec chroot . sh -c 'umount /old_root; exec /sbin/init'
<dev/console >dev/console 2>&1
SEE ALSO chroot(1), mount(8), pivot_root(2), umount(8)AVAILABILITY
The pivot_root command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
Linux Feb 23, 2000 PIVOT_ROOT(8)