10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
Hello Experts,
In one of my shell script, I've been trying to calculate mod and saving it in a variable, below is what I have tried but it isn't working.
Any help appreciated!!!
#!/bin/bash
num1=4
num2=3
echo "Number one is $num1"
echo "Number two is $num2"
mod_final=$(( echo "num1%num2"... (7 Replies)
Discussion started by: mukulverma2408
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2. Shell Programming and Scripting
So, I've been playing with speeding up some analysis we do by using multiple threads of awk (actually, mawk, but code-compatible as far as I use it) on multiple CPU cores. So, I have a big data file and I have several copies of exactly the same processor script, written in mawk. I also have a... (8 Replies)
Discussion started by: treesloth
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3. Shell Programming and Scripting
Hello,
Although I have found similar questions, I could not find advice that could help with our problem.
The issue:
We have a few thousands text files (books).
Each book has many chapters. Each chapter is identified by a cite-key. We need
to split each of those book files by... (4 Replies)
Discussion started by: samask
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4. Shell Programming and Scripting
I'm trying to make a sed substitution where the substitution pattern is an environment variable to be expanded, but the variable contains a "slash".
sed -e 's/<HOME_DIRECTORY>/'$HOME'/'This gives me the following error:
sed: -e expression #1, char 21: unknown option to `s'Obviously this is... (2 Replies)
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5. Shell Programming and Scripting
Hi,
I have problems when you save a variable of a command. I have put the following line:
CONEXION_BAGDAD = $ (grep-c "Please login with USER and PASS" $ LOG_FILE_BAGDAD)
But I returned the following error:
syntax error at line 67: `CONEXION_BAGDAD = $ 'unexpected
Because it can happen?... (2 Replies)
Discussion started by: danietepa
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6. Shell Programming and Scripting
I need to capture the homedir using the ssh command and then saving it to a variable.
The results from the following command is what I need to capture to a variable:
NOTE: the value I'm getting back is also incorrect. as it seems to be getting the home dir from the local server and not the... (2 Replies)
Discussion started by: reneuend
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7. Shell Programming and Scripting
Hi
I get the following error while executing the shell script. I did not get an error when I ran the script in a different environment (unix server).
str-token.ksh: 0403-057 Syntax error at line 20 : `(' is not expected.
This is the line which gives error
string=(${pos_array})
Please find... (3 Replies)
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8. UNIX for Dummies Questions & Answers
Hello,
I have a shell script containing a command string in the following format:
command1 | command2 | cut -c9-16
The output from this is a record number (using characters 9-16 of the original output string) e.g. ORD-1234
I wish to save this value to a variable for use in later commands... (4 Replies)
Discussion started by: philjo
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9. Shell Programming and Scripting
hi all i am trying to save an awk value into an array in bash:
total=`awk '{sum+=$3} END {print sum}' "$count".txt"`
((count++))
the above statement is in a while loop..
$count is to keep track of file numbers (1.txt,2.txt,3.txt,etc.)
i get the following error:
./lines1:... (1 Reply)
Discussion started by: npatwardhan
1 Replies
10. Shell Programming and Scripting
How would I pass awk output to a perl variable?
For example, I want to save the value in the 4th column into the variable called test. My best guess is something as follow, but I am sure this isn't correct.
$test = system("awk '/NUMBER/{print \$4}' $_"); (8 Replies)
Discussion started by: userix
8 Replies
SH(1) General Commands Manual SH(1)
NAME
sh, ., break, case, cd, continue, eval, exec, exit, export, for, if, read, readonly, set, shift, trap, umask, wait, while - shell
SYNOPSIS
sh [-eiknqstvxu] [-c str] [file]
OPTIONS
-c Execute the commands in str
-e Quit on error
-i Interactive mode; ignore QUIT, TERMINATE, INTERRUPT
-k Look for name=value everywhere on command line
-n Do not execute commands
-q Change qflag from sig_ign to sig_del
-s Read commands from standard input
-t Exit after reading and executing one command
-v Echo input lines as they are read
-x Trace
-u Unset variables
EXAMPLES
sh script # Run a shell script
DESCRIPTION
Sh is the shell, which forms the user's main interface with the system. On startup, the shell reads /etc/profile and $HOME/.profile, if
they exist, and executes any commands they contain. The Minix shell has most of the features of the V7 (Bourne) shell, including redirect-
ion of input and output, pipes, magic characters, background processes, and shell scripts. A brief summary follows, but whole books have
been written on shell programming alone.
Some of the more common notations are:
date # Regular command
sort <file # Redirect stdin (standard input)
sort <file1 >file2 # Redirect stdin and stdout
cc file.c 2>error # Redirect stderr
a.out >f 2>&1 # Combine standard output and standard error
sort <file1 >>file2 #Append output to file2
sort <file1 >file2 & #Background job
(ls -l; a.out) & # Run two background commands sequentially
sort <file | wc # Two-process pipeline
sort <f | uniq | wc # Three-process pipeline
ls -l *.c # List all files ending in .c
ls -l [a-c]* # List all files beginning with a, b, or c
ls -l ? # List all one-character file names
ls ? # List the file whose name is question mark
ls '???' # List the file whose name is three question marks
v=/usr/ast # Set shell variable v
ls -l $v # Use shell variable v
PS1='Hi! ' # Change the primary prompt to Hi!
PS2='More: ' # Change the secondary prompt to More:
ls -l $HOME # List the home directory
echo $PATH # Echo the search path
echo $? # Echo exit status of previous command in decimal
echo $$ # Echo shell's pid in decimal
echo $! # Echo PID of last background process
echo $# # Echo number of parameters (shell script)
echo $2 # Echo second parameter (shell script)
echo "$2" # Echo second parameter without expanding spaces
echo $* # Echo all parameters (shell script)
echo $@ # Echo all parameters (shell script)
echo "$@" # Echo all parameters without expanding spaces
The shell uses the following variables for specific purposes:
SHELL the path of the current shell
HOME the default value for the cd(1) command
PATH the directories to be searched to find commands
IFS the internal field separators for command strings
PS1 the primary shell prompt
PS2 the secondary shell prompt
There are various forms of substitution on the shell command line:
`...` Command string between back-quotes is replaced by its output
"..." Permits variable substitution between quotes
'...' Inhibits variable substitution between quotes
$VAR Replaced by contents of variable VAR
${VAR} Delimits variable VAR from any following string
The expressions below depend on whether or not VAR has ever been set. If VAR has been set, they give:
${VAR-str} Replace expression by VAR, else by str
${VAR=str} Replace expression by VAR, else by str and set VAR to str
${VAR?str} Replace expression by VAR, else print str and exit shell
${VAR+str} Replace expression by str, else by null string
If a colon is placed after VAR, the expressions depend on whether or not VAR is currently set and non-null.
The shell has a number of built-in commands:
: return true status
. fn execute shell script fn on current path
break [n] break from a for, until or while loop; exit n levels
continue [n] continue a for, until or while loop; resume nth loop
cd [dir] change current working directory; move to $HOME
eval cmd rescan cmd, performing substitutions
eval rescan the current command line
exec cmd execute cmd without creating a new process
exec <|> with no command name, modify shell I/O
exit [n] exit a shell program, with exit value n
export [var] export var to shell's children; list exported variables
pwd print the name of the current working directory
read var read a line from stdin and assign to var
readonly [var] make var readonly; list readonly variables
set -f set shell flag (+f unsets flag)
set str set positional parameter to str
set show the current shell variables
shift reassign positional parameters (except ${0}) one left
times print accumulated user and system times for processes
trap arg sigs trap signals sigs and run arg on receipt
trap list trapped signals
umask [n] set the user file creation mask; show the current umask
wait [n] wait for process pid n; wait for all processes
The shell also contains a programming language, which has the following operators and flow control statements:
# Comment The rest of the line is ignored
= Assignment Set a shell variable
&& Logical AND Execute second command only if first succeeds
|| Logical OR Execute second command only if first fails
(...) Group Execute enclosed commands before continuing
for For loop (for ... in ... do ... done)
case Case statement ((case ... ) ... ;; ... esac)
esac Case statement end
while While loop (while ... do ... done)
do Do/For/While loop start (do ... until ...)
done For/While loop end
if Conditional statement (if ... else ... elif ... fi)
in For loop selection
then Conditional statement start
else Conditional statement alternative
elif Conditional statement end
until Do loop end
fi Conditional statement end
SEE ALSO
echo(1), expr(1), pwd(1), true(1).
SH(1)