Okay the answer to this may be really simple but I have been searching for a while and I can't figure it out. I have a variable called "tmessagef". The variable is formatted like:
value1*value2*vlaue3*value4*value5
The only part of the variable I want is value 5. I am currently using the following code but it only prints each value and doesn't save them to a variable:
OIFS=$IFS
IFS='*'
arr2=$tmessagef
for x in $arr2
do
echo "$x"
done
IFS=$OIFS
What I want to do is get the 5th line that the echo command produces and save that to a variable called "tmessage". How would I go about doing this?
Thanks in advance.
Array manipulation:
OIFS="$IFS" IFS='*' Y=($X)
x=${Y[${#Y[#]}-1]}
IFS="$OIFS"
For this very specific scenario (where you only want to extract the value at the very end), you can use parameter expansion
echo "${word##*\*}"
or assign it to a variable instead of using "echo".
Explanation:
## removes the longest substring anchored at the beginning that matches the pattern
* matches any number of any character
\* matches a literal asterisk
So basically, remove the longest substring that ends with an asterisk.
I believe mcalex's comment should answer it:
Change echo "$x" to tmessage="$x". At the end of the loop $val will contain the last value
IFS=* read -r _{,,,} tmessage _ <<<"$tmessagef"
or
[[ $tmessagef =~ ^(.*\*){4}(.*)\* ]]; tmessage=${BASH_REMATCH[2]}
Read http://mywiki.wooledge.org/BashFAQ/001 and the trillion other answers to this question.
Don't use echo for this. If you have output that needs saving, see: http://mywiki.wooledge.org/BashFAQ/002
Can you use cut?
VAL=`echo 'value1*value2*vlaue3*value4*value5' | cut -f5 -d'*'`
Related
I need help writing a script to do the following stated below in part a.
The following code will output all of the words found in $filename, each word on a separate line.
for word in “cat $filename”
do
echo $word
done
a. Write a new script which receives two parameters. The first is a file’s name ($1 instead of $filename) and the second is a word you want to search for ($2). Inside the for loop, instead of echo $word, use an if statement to compare $2 to $word. If they are equal, add one to a variable called COUNT. Before the for loop, initialize COUNT to 0 and after the for loop, output a message that tells the user how many times $2 appeared in $1. That is, output $COUNT, $2 and $1 in an echo statement but make sure you have some literal words in here so that the output actually makes sense to the user. HINTS: to compare two strings, use the notation [ $string1 == $string2 ]. To add one to a variable, use the notation X=$((X+1)). If every instruction is on a separate line, you do not need any semicolons. Test your script on /etc/fstab with the word defaults (7 occurrences should be found)
This is what I got so far, but it does not work right. It says it finds 0 occurrences of the word "defaults" in /etc/fstab. I am sure my code is wrong but can't figure out the problem. Help is appreciated.
count=0
echo “what word do you want to search for?: “
read two
for word in “cat $1”
do
if [ “$two” == “$word” ]; then
count=$((count+1))
fi
done
echo $two appeared $count times in $1
You need to use command substitution, you were looping over this string: cat first_parameter.
for word in $(cat "$1")
Better way to do this using grep, paraphrasing How do I count the number of occurrences of a word in a text file with the command line?
grep -o "\<$two\>" "$1" | wc -l
$cat list
Hi
welcome
one
two
good evening
Value1="two"
value2="evening"
For above file values, output should be echo "values are present one after the other line"
Need to know the if condition command to check if both variable values occur one after the other in a file.
If both variable values occur one line after other in a file, then echo some statement.
for example:
$cat list
Hi
two
one
three
good evening
in above condition, both variable value are not present one after the other line so output should be echo "values are not present one after the other line"
With awk you could write something like this:
awk -F= '$1=="Value1"{l=NR}$1=="value2"&&NR==l+1{print "ok"}' file
#!/bin/bash
Value1="two"
value2="evening"
while read line; do
if [[ "$Value1" == *"$line"* ]];then
read anotherline
if [[ "$anotherline" == *"$value2"* ]];then
echo "values are present one after the other line"
fi
fi
done < list
If you want exact string match then remove * wildcards and use single brackets
I am new to AIX and I have trouble understanding the codes stated in the shell script as shown below, I have a few questions.
if [ "$OutChlName" != "" ] ; then
echo START CHANNEL \($OutChlName\)
fi
For the first line, what does the "" mean, does it mean null?
\($OutChlName\) - is there any way to convert this to a batch file format.
Is it right to say that fi is the end tag of if?
Thank you.
The echo is only wanted when the variable OutChkName is filled.
The string is compared with an empty string.
When you read man test, you can find the alternative if [ -n "$OutChlName" ].
echo with double quotes
Within quotes you do not need the backslashes.
echo "START CHANNEL ($OutChlName)"
My echo behaves different when the OutChlName variable has special characters like newlines or *. I think my syntax is a slight bugfix, but when you do not want to change the original behaviour, you can use
echo "START CHANNEL ("$OutChlName")"
Using backslashes is also a valid syntax (batch format).
fi ends if
Also esac ends case, and done ends do (Odd, it should have been od).
I have the following format for filenames: filename_1234.svg
How can I retrieve the numbers preceded by an underscore and followed by a dot. There can be between one to four numbers before the .svg
I have tried:
width=${fileName//[^0-9]/}
but if the fileName contains a number as well, it will return all numbers in the filename, e.g.
file6name_1234.svg
I found solutions for two underscores (and splitting it into an array), but I am looking for a way to check for the underscore as well as the dot.
You can use simple parameter expansion with substring removal to simply trim from the right up to, and including, the '.', then trim from the left up to, and including, the '_', leaving the number you desire, e.g.
$ width=filename_1234.svg; val="${width%.*}"; val="${val##*_}"; echo $val
1234
note: # trims from left to first-occurrence while ## trims to last-occurrence. % and %% work the same way from the right.
Explained:
width=filename_1234.svg - width holds your filename
val="${width%.*}" - val holds filename_1234
val="${val##*_}" - finally val holds 1234
Of course, there is no need to use a temporary value like val if your intent is that width should hold the width. I just used a temp to protect against changing the original contents of width. If you want the resulting number in width, just replace val with width everywhere above and operate directly on width.
note 2: using shell capabilities like parameter expansion prevents creating a separate subshell and spawning a separate process that occurs when using a utility like sed, grep or awk (or anything that isn't part of the shell for that matter).
Try the following code :
filename="filename_6_1234.svg"
if [[ "$filename" =~ ^(.*)_([^.]*)\..*$ ]];
then
echo "${BASH_REMATCH[0]}" #will display 'filename_6_1234.svg'
echo "${BASH_REMATCH[1]}" #will display 'filename_6'
echo "${BASH_REMATCH[2]}" #will display '1234'
fi
Explanation :
=~ : bash operator for regex comparison
^(.*)_([^.])\..*$ : we look for any character, followed by an underscore, followed by any character, followed by a dot and an extension. We create 2 capture groups, one for before the last underscore, one for after
BASH_REMATCH : array containing the captured groups
Some more way
[akshay#localhost tmp]$ filename=file1b2aname_1234.svg
[akshay#localhost tmp]$ after=${filename##*_}
[akshay#localhost tmp]$ echo ${after//[^0-9]}
1234
Using awk
[akshay#localhost tmp]$ awk -F'[_.]' '{print $2}' <<< "$filename"
1234
I would use
sed 's!_! !g' | awk '{print "_" $NF}'
to get from filename_1234.svg to _1234.svg then
sed 's!svg!!g'
to get rid of the extension.
If you set IFS, you can use Bash's build-in read.
This splits the filename by underscores and dots and stores the result in the array a.
IFS='_.' read -a a <<<'file1b2aname_1234.svg'
And this takes the second last element from the array.
echo ${a[-2]}
There's a solution using cut:
name="file6name_1234.svg"
num=$(echo "$name" | cut -d '_' -f 2 | cut -d '.' -f 1)
echo "$num"
-d is for specifying a delimiter.
-f refers to the desired field.
I don't know anything about performance but it's simple to understand and simple to maintain.
I have a variable in a shell script in which I'd like to format the data. The variable stores new data during every iteration of a loop. Each time the new data is stored, I'd like to insert a new line character. Here is how I'm trying to store the data into the variable.
VARIABLE="$VARIABLE '\n' SomeData"
Unfortunately, the output includes the literal '\n' Any help would be appreciative.
Try $'\n':
VAR=a
VAR="$VAR"$'\n'b
echo "$VAR"
gives me
a
b
A common technique is:
nl='
'
VARIABLE="PreviousData"
VARIABLE="$VARIABLE${nl}SomeData"
echo "$VARIABLE"
PreviousData
SomeData
Also common, to prevent inadvertently having your string start with a newline:
VARIABLE="$VARIABLE${VARIABLE:+$nl}SomeData"
(The expression ${VARIABLE:+$nl} will expand to a newline if and only if VARIABLE is set and non-empty.)
VAR="one"
VAR="$VAR.\n.two"
echo -e $VAR
Output:
one.
.two
Other than $'\n' you can use printf also like this:
VARIABLE="Foo Bar"
VARIABLE=$(printf "${VARIABLE}\nSomeData")
echo "$VARIABLE"
OUTPUT:
Foo Bar
SomeData
I had a problem with all the other solutions: when using a # followed by SPACE (quite common when writing in Markdown) both would get split onto a new line.
So, another way of doing it would involve using single quotes so that the "\n" get rendered.
FOO=$'# Markdown Title #\n'
BAR=$'Be *brave* and **bold**.'
FOOBAR="$FOO$BAR"
echo "$FOOBAR"
Output:
# Markdown Title #
Be *brave* and **bold**.
Single quote All special characters between these quotes lose their
special meaning.https://www.tutorialspoint.com/unix/unix-quoting-mechanisms.htm
So the syntax you use does something different that you want to achieve.
This is what you need:
The $'\X' construct makes the -e option in echo unnecessary.
https://linux.die.net/abs-guide/escapingsection.html
echo -e "something\nsomething"
or
echo "something"$'\n'"something"
It's a lot simpler than you think:
VARIABLE="$VARIABLE
SomeData"
Building upon the first two solutions, I'd do like shown below. Concatenating strings with the '+=' operator, somehow looks clearer to me.
Also rememeber to use printf as opposed to echo, you will save yourself so much trouble
sometext="This is the first line"
sometext+=$'\n\n'
sometext+="This is the second line AFTER the inserted new lines"
printf '%s' "${sometext}"
Outputs:
This is the first line
This is the third line AFTER the inserted new line
Your problem is in the echo command, in ash you have to use the option -e to expand special characters. This should work for you:
VAR="First line"
VAR="$VAR\nSecond line"
echo -e $VAR
This outputs
First line
Second line