Sponsored Content
Top Forums Shell Programming and Scripting Need to create a simple script using MD5, SSH... Post 302503085 by Corona688 on Wednesday 9th of March 2011 04:11:03 PM
Old 03-09-2011
Okay, so we're feeding the output of /usr/local/bin/hosts into the loop like this:

Code:
/usr/local/bin/hosts | while read LINE
do
        echo "Got $LINE"
done

...but anything in the loop can read read from that, not just the 'while' bit. If you do this:
Code:
/usr/local/bin/hosts | while read LINE
do
        cat > /dev/null # Read and throw away the rest of the lines
        echo "Got $LINE"
done

...you get nothing but the first line.

I didn't expect the md5 command to read anything except the file it was given; that's not just the way md5sum works but the traditional way for UNIX commands to operate. Some read standard input when given no files, and some read standard input when told to read from -. I gave it a filename, and it read from the file, and when it finished that it read from the list, too! Throwing it all away and putting it into the checksum. I had to force it to read from /dev/null instead, which is a "special" file that always does nothing.

---------- Post updated at 03:11 PM ---------- Previous update was at 03:02 PM ----------

Quote:
Originally Posted by Chubler_XL
Think they all match because $TMP still has result from local hash or previous host
Sorry, but that's completely wrong. > always truncates the file, so the temp file was always completely replaced each time ssh was called. You could hardly expect your ">$TMP" to work if > didn't work that way! You have to use >> to append.

The defensive quoting is a good idea though.
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

How to create md5 Hash variable?

I have a script that runs the grub-md5-crypt command based on whether the pass_value variable is a non-zero string. The md5 hash is being created in the /opt/hostconfigs/$HOST file, but I can't echo $md5_value. It is blank. Is there a way to create and echo a md5 hash variable? if then... (1 Reply)
Discussion started by: cstovall
1 Replies

2. Shell Programming and Scripting

Modifying simple commands to create a script

Can anyone direct me to a resource that explains scripting in simple terms? I have visited many sites and browsed this forum and have yet to find simple explanations. (8 Replies)
Discussion started by: rocinante
8 Replies

3. Shell Programming and Scripting

Simple Script to create folders

Hi I want to write a small script that will create folders named from `AAAA' all the way to `ZZZZ'. That is: `AAAA' `AAAB' `AAAC' ... `AABA' `AABB' `AABC' ... `ABAA' `ABAB' `ABAC' ... `ABBA' ... `ZZZZ' (4 Replies)
Discussion started by: ksk
4 Replies

4. Shell Programming and Scripting

Simple SSH script

I have several unix servers, I need to logon to each server and find out if an id exists on that server. I need a simple script for this, i have come up with the following script, but I cannot bring the output of a child process on the remote server. for i in `cat SERVER_LIST` do ssh $i... (5 Replies)
Discussion started by: ramky79
5 Replies

5. Solaris

How to create a simple background script on Solaris

I have a local account for a unix server. The idle timeout for the account is around 10 mins. I have to login to the server multiple times during the day. Is there a way to increase the idle timeout or may be a script that I can run on background so it is not idle. Something like echo date every 9... (3 Replies)
Discussion started by: vinaysa
3 Replies

6. Shell Programming and Scripting

How to create a simple shell script to backup

Hello - I am in process of deleting many files which are older than 4 weeks. For example I am inside: /subsystem/prod/ Files are with various extentions, but anything older than 4 weeks should be deleted. What would be the most simplest script to acheive this? (4 Replies)
Discussion started by: DallasT
4 Replies

7. Shell Programming and Scripting

Create md5 sums and archive the resulting md5 files

Hello everyone, I am looking to basically creating md5sum files for all iso files in a directory and archive the resulting md5 files into a single archive in that very same directory. I worked out a clumsy solution such as: #find files for which md5sum are to be created and store the... (1 Reply)
Discussion started by: SurfTranquille
1 Replies

8. Shell Programming and Scripting

How to create a simple copy script?

Guys I want to do this: copy: /var/router/system1/config/backup/install.put /var/router/system2/config/backup/install.put /var/router/system3/config/backup/install.put /var/router/system4/config/backup/install.put into: /var/router/system1/config/install.dat... (22 Replies)
Discussion started by: DallasT
22 Replies

9. Shell Programming and Scripting

Create simple script

Dear all, I have a directory named A and some subdirectories named B, C, D with .xml files. I want to use the following command to strip the file. sed -re ':start s/<*>//g; /</ {N; b start}' file.xml > file.xml At the same time, I want to remove the blank lines using sed '/^$/d' How can... (6 Replies)
Discussion started by: corfuitl
6 Replies

10. Shell Programming and Scripting

Help making simple perl or bash script to create a simple matrix

Hello all! This is my first post and I'm very new to programming. I would like help creating a simple perl or bash script that I will be using in my work as a junior bioinformatician. Essentially, I would like to take a tab-delimted or .csv text with 3 columns and write them to a "3D" matrix: ... (16 Replies)
Discussion started by: torchij
16 Replies
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)
All times are GMT -4. The time now is 05:56 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy