I'm totally new to writing code with shell script.
This is my code:
#!/bin/bash
echo -n "Output to $2 "
# set counter
count=1
# zap output file
> $2
# Loop
while [ $count -le $1 ]
do
# generate some random text
randomnumber=`od -A n -t d -N 1 /dev/urandom`
randomtext=`cat /dev/urandom | tr -cd "[:alnum:]" | head -c $randomnumber`
# generate a random number
randomnumber=`od -A n -t d -N 1 /dev/urandom`
# output to file
echo "$count,$randomtext,$randomnumber" | sed -e "s: *::g" >> $2
# increment counter
count=$(($count + 1))
if [ $(($count % 500)) -eq 0 ]
then
echo -n "." fi
done
echo " Output complete"
And this is my error:
Line 2: ambiguous redirect and Line 14: unary operator expected.
Can anybody help me to understand why I having that error?
As #GlennJackman points out, the lines are not matching the code, hence I am guessing the following:
The ambiguous redirection is on line 6: To truncate a file, you
should use truncate -s0 $2
For the unary operator error, I bet on line 21: either put a linefeed
or a semicolon ; before fi
Try the following:
#!/bin/bash
echo -n "Output to $2 "
# set counter
count=1
# zap output file
truncate -s0 $2
# Loop
while [ $count -le $1 ]
do
# generate some random text
randomnumber=`od -A n -t d -N 1 /dev/urandom`
randomtext=`cat /dev/urandom | tr -cd "[:alnum:]" | head -c $randomnumber`
# generate a random number
randomnumber=`od -A n -t d -N 1 /dev/urandom`
# output to file
echo "$count,$randomtext,$randomnumber" | sed -e "s: *::g" >> $2
# increment counter
count=$(($count + 1))
if [ $(($count % 500)) -eq 0 ]
then
echo -n "."
fi
done
echo " Output complete"
Related
I have a string like 1001.2001.3001.5001.6001 or 1001-2001-3001-5001-6001. How to extract the 4th string i.e., 5001, add a value like 121 to it and put it back in the same string. The output should be like 1001.2001.3001.5122.6001 or 1001-2001-3001-5122-6001. I have to achieve this in Linux bash scripting.
Try this
#!/bin/bash
str=$1
if [[ $(echo $str | grep '\.' | wc -l) == 1 ]]
then
str1=$(echo $str | cut -d '.' -f 1,2,3)
str2=$(echo $str | cut -d '.' -f 4 | awk {'print $1+121'})
str3=$(echo $str | cut -d '.' -f 5)
echo $str1.$str2.$str3
elif [[ $(echo $str | grep - | wc -l) == 1 ]]
then
str1=$(echo $str | cut -d '-' -f 1,2,3)
str2=$(echo $str | cut -d '-' -f 4 | awk {'print $1+121'})
str3=$(echo $str | cut -d '-' -f 5)
echo $str1-$str2-$str3
else
echo "do nothing"
fi
Pass a string as parameter
No pipes, no forks, no cutting, no awking, just plain POSIX shell:
$ s=1001.2001.3001.5001.6001
$ oldIFS=$IFS
$ IFS=.-
$ set -- $s
$ case $s in
> (*.*) echo "$1.$2.$3.$(($4 + 121)).$5";;
> (*-*) echo "$1-$2-$3-$(($4 + 121))-$5";;
> esac
1001.2001.3001.5122.6001
$ IFS=$oldIFS
One liner
value=121 ; str='1001.2001.3001.5001.6001' ; token="$(echo "$str" | cut -f 4 -d '.')" ; newtoken=$(( $token + $value )) ; newstr="$(echo "$str" | sed -e "s/$token/$newtoken/g" | tr '.' '-')" ; echo "$newstr"
Breakdown:
value=121 # <- Increment
str='1001.2001.3001.5001.6001' # <- Initial String
token="$(echo "$str" | cut -f 4 -d '.')" # <- Extract the 4th field with . sep
newtoken=$(( $token + $value )) # <- Add value and save to $newtoken
newstr="$(echo "$str" \
| sed -e "s/$token/$newtoken/g" \
| tr '.' '-')" # <- Replace 4th field with $newtoken
# and translate "." to "-"
echo "$newstr" # <- Echo new string
Works in:
Bash
sh
FreeBSD
Busybox
Using out of the box tools
If the field separator can either be . or -, then do something like
echo "1001.2001.3001.5001.6001" | awk 'BEGIN{FS="[.-]";OFS="-"}{$4+=121}1'
1001-2001-3001-5122-6001
However, if you need to match the regex FS or field separator with OFS then you need to have gawk installed
echo "1001.2001.3001.5001.6001" |
gawk 'BEGIN{FS="[.-]"}{split($0,a,FS,seps)}{$4+=121;OFS=seps[1]}1'
1001.2001.3001.5122.6001
Though resetting the argument list with the values is probably the preferred way, or by setting IFS to the delimiter and reading the values into an array and adding the desired value to the array index at issue, you can also do it with a simple loop to look for the delimiters and continually skipping characters until the desired segment is found (4 in you case -- when the delimiter count is 3). Then simply appending the digit at each array index until your next delimiter is found will give you the base value. Simply adding your desired 121 to the completed number completes the script, e.g.
#!/bin/bash
str=${1:-"1001.2001.3001.5001.6001"} ## string
ele=${2:-4} ## element to add value to [1, 2, 3, ...]
add=${3:-121} ## value to add to element
cnt=0 ## flag to track delimiters found
num=
## for each character in str
for ((i = 0; i < ${#str}; i++))
do
if [ "${str:$i:1}" = '.' -o "${str:$i:1}" = '-' ] ## is it '.' or '-'
then
(( cnt++ )) ## increment count
(( cnt == ele )) && break ## if equal to ele, break
## check each char is a valid digit 0-9
elif [ "0" -le "${str:$i:1}" -a "${str:$4i:1}" -le "9" ]
then
(( cnt == (ele - 1) )) || continue ## it not one of interest, continue
num="$num${str:$i:1}" ## append digit to num
fi
done
((num += add)) ## add the amount to num
printf "num: %d\n" $num ## print results
Example Use/Output
$ bash parsenum.sh
num: 5122
$ bash parsenum.sh "1001.2001.3001.5001.6001" 2
num: 2122
$ bash parsenum.sh "1001.2001.3001.5001.6001" 2 221
num: 2222
Look things over and let me know if you have any questions.
For a homework assignment I have to Take the results from the grep command, and write out up to the first 5 of them, numbering them from 1 to 5. (Print the number, then a space, then the line from grep.) If there are no lines, print a message saying so. So far I managed to store the grep command in an array but this is where I've gotten stuck: Can anyone provide guidance as to how to proceed in printing this as stated above
pattern="*.c"
fileList=$(grep -l "main" $pattern)
IFS=$"\n"
declare -a array
array=$fileList
for x in "${array[#]}"; do
echo "$x"
done
you can grep options -c and -l
pattern="*.c"
searchPattern="main"
counter=1
while read -r line ; do
IFS=':' read -r -a lineInfo <<< "$line"
if [[ $counter > 5 ]]; then
exit 1
fi
if [[ ${lineInfo[1]} > 0 ]]; then
numsOfLine=""
while read -r fileline ; do
IFS=':' read -r -a fileLineInfo <<< "$fileline"
numsOfLine="$numsOfLine ${fileLineInfo[0]} "
done < <(grep -n $searchPattern ${lineInfo[0]})
echo "$counter ${lineInfo[0]} match on lines: $numsOfLine"
let "counter += 1"
else
echo "${lineInfo[0]} no match lines"
fi
done < <(grep -c $searchPattern $pattern)
If you're only allowed to use grep and bash(?):
pattern="*.c"
fileList=($(grep -l "main" $pattern))
if test ${#fileList[#]} = 0 ; then
echo "No results"
else
n=0
while test $n -lt ${#fileList[#]} -a $n -lt 5 ; do
i=$n
n=$(( n + 1 ))
echo "$n ${fileList[$i]}"
done
fi
If you are allowed to use commands in addition to grep, you can pipe the results through nl to add line numbers, then head to limit the results to the first 5 lines, then a second grep to test if there were any lines. For example:
if ! grep -l "main" $pattern | \
nl -s ' ' | sed -e 's/^ *//' | \
head -n 5 | grep '' ; then
echo "No results"
fi
I want to say output lines 5 - 10 of a file, as arguments passed in.
How could I use head and tail to do this?
where firstline = $2 and lastline = $3 and filename = $1.
Running it should look like this:
./lines.sh filename firstline lastline
head -n XX # <-- print first XX lines
tail -n YY # <-- print last YY lines
If you want lines from 20 to 30 that means you want 11 lines starting from 20 and finishing at 30:
head -n 30 file | tail -n 11
#
# first 30 lines
# last 11 lines from those previous 30
That is, you firstly get first 30 lines and then you select the last 11 (that is, 30-20+1).
So in your code it would be:
head -n $3 $1 | tail -n $(( $3-$2 + 1 ))
Based on firstline = $2, lastline = $3, filename = $1
head -n $lastline $filename | tail -n $(( $lastline -$firstline + 1 ))
Aside from the answers given by fedorqui and Kent, you can also use a single sed command:
#!/bin/sh
filename=$1
firstline=$2
lastline=$3
# Basics of sed:
# 1. sed commands have a matching part and a command part.
# 2. The matching part matches lines, generally by number or regular expression.
# 3. The command part executes a command on that line, possibly changing its text.
#
# By default, sed will print everything in its buffer to standard output.
# The -n option turns this off, so it only prints what you tell it to.
#
# The -e option gives sed a command or set of commands (separated by semicolons).
# Below, we use two commands:
#
# ${firstline},${lastline}p
# This matches lines firstline to lastline, inclusive
# The command 'p' tells sed to print the line to standard output
#
# ${lastline}q
# This matches line ${lastline}. It tells sed to quit. This command
# is run after the print command, so sed quits after printing the last line.
#
sed -ne "${firstline},${lastline}p;${lastline}q" < ${filename}
Or, to avoid any external utilites, if you're using a recent version of bash (or zsh):
#!/bin/sh
filename=$1
firstline=$2
lastline=$3
i=0
exec <${filename} # redirect file into our stdin
while read ; do # read each line into REPLY variable
i=$(( $i + 1 )) # maintain line count
if [ "$i" -ge "${firstline}" ] ; then
if [ "$i" -gt "${lastline}" ] ; then
break
else
echo "${REPLY}"
fi
fi
done
try this one-liner:
awk -vs="$begin" -ve="$end" 'NR>=s&&NR<=e' "$f"
in above line:
$begin is your $2
$end is your $3
$f is your $1
Save this as "script.sh":
#!/bin/sh
filename="$1"
firstline=$2
lastline=$3
linestoprint=$(($lastline-$firstline+1))
tail -n +$firstline "$filename" | head -n $linestoprint
There is NO ERROR HANDLING (for simplicity) so you have to call your script as following:
./script.sh yourfile.txt firstline lastline
$ ./script.sh yourfile.txt 5 10
If you need only line "10" from yourfile.txt:
$ ./script.sh yourfile.txt 10 10
Please make sure that:
(firstline > 0) AND (lastline > 0) AND (firstline <= lastline)
Working in a shell script here, trying to count the number of words/characters/lines in a file without using the wc command. I can get the file broken into lines and count those easy enough, but I'm struggling here to get the words and the characters.
#define word_count function
count_stuff(){
c=0
w=0
l=0
local f="$1"
while read Line
do
l=`expr $line + 1`
# now that I have a line I want to break it into words and characters???
done < "$f"
echo "Number characters: $chars"
echo "Number words: $words"
echo "Number lines: $line"
}
As for characters, try this (adjust echo "test" to where you get your output from):
expr `echo "test" | sed "s/./ + 1/g;s/^/0/"`
As for lines, try this:
expr `echo -e "test\ntest\ntest" | sed "s/^.*$/./" | tr -d "\n" | sed "s/./ + 1/g;s/^/0/"`
===
As for your code, you want something like this to count words (if you want to go at it completely raw):
while read line ; do
set $line ;
while true ; do
[ -z $1 ] && break
l=`expr $l + 1`
shift ;
done ;
done
You can do this with the following Bash shell script:
count=0
for var in `cat $1`
do
count=`echo $count+1 | bc`
done
echo $count
i found some freaky error. I want to increment a counter, but the variable isnt visible outside the while do.
The script as follows:
## $1 - The file which should be examined
## $2 - The time passed between the checks. If $2 is 5 then all lines from the last 5 minutes are taken
## $3 - The Errormessage to search for
outputOK="OK - nothing happened"
output_logcheck=0;
errlines="";
cat $1 | grep "$3" | while read line
do
linedate=`date -d "$(echo $line | cut -d " " -f 2)" '+%s'`
nowdate=`date '+%s'`
if [ $(( $nowdate - (60 * $2) )) -le $linedate ]
then
$output_logcheck=$[$output_logcheck+1]
$errlines="${errlines} -- ${line}"
fi
done;
if [ $output_logcheck -eq 0 ]
then
echo $outputOK
else
echo "CRITICAL - There are -= ${output_logcheck} =- $3 -- Lines: $errlines"
fi
So i dont know what else to try.
Thanks in advance.
The problem is that pipe create a SubShell.
change
cat $1 | grep "$3" | while read line
do
...
done
to
while read line
do
...
done <(cat $1 | grep "$3")
As noted, the Bash shell, creates a subshell whenever a pipe is opened to a loop. In that case, variables within the loop are local to the loop.
One kludge is to substitute (if possible) a Korn ('ksh') shell for the Bash one.
Try something like:
## $1 - The file which should be examined
## $2 - The time passed between the checks. If $2 is 5 then all lines from the last 5 minutes are taken
## $3 - The Errormessage to search for
outputOK="OK - nothing happened"
outfile="/tmp/result.$$"
trap { rm $outfile } 0 1 2 3
cat $1 | grep "$3" | (output_logcheck=0; errlines=""; while read line
do
linedate=`date -d "$(echo $line | cut -d " " -f 2)" '+%s'`
nowdate=`date '+%s'`
if [ $(( $nowdate - (60 * $2) )) -le $linedate ]
then
$output_logcheck=$[$output_logcheck+1]
$errlines="${errlines} -- ${line}"
fi
done; echo $output_logcheck ":" $errlines > $outfile)
output_logcheck=`cat $outfile| cut -f1 -d:`
errlines=`cat $outfile|cut -f2 -d:`
if [ $output_logcheck -eq 0 ]
then
echo $outputOK
else
echo "CRITICAL - There are -= ${output_logcheck} =- $3 -- Lines: $errlines"
fi
while is executed in a separate process. Variables that are changed in the context of that process still hold their unchanged valus in the parent process.