I am trying to declare an array in my shell script and then have written a for loop to access those array elements into another file. But it is only taking the first element. I've tried the below :
raw_cd=(1150 1151)
i=0
for i in "${raw_cd[#]}"
do
grep -wr "${raw_cd[#]}" file1.txt > /opt/tmp/raw.txt
echo "$i"
done
It is taking only the first element 1150 and also giving output as :-
file1.txt:|1150|
file1.txt:|1150|
file1.txt:|1150|
where am i doing wrong?
for does not deal with indices, just raw values. Thus,
raw_cd=(1150 1151)
for i in "${raw_cd[#]}"
do
echo "$i"
done
will print
1150
1151
If you want to use indices, you need to produce them yourself:
raw_cd=(1150 1151)
for i in $(seq "${#raw_cd[#]}")
do
echo "$i": "${raw_cd[$i - 1]}"
done
will produce
1: 1150
2: 1151
Even better, you can directly get keys like this, without seq (this will work even on associative arrays):
raw_cd=(1150 1151)
for i in "${!raw_cd[#]}"
do
echo "$i": "${raw_cd[$i]}"
done
Related
In bash,
I have a string, I want to convert in array and use it in a for loop but skipping the first element. The code below does not works:
build_string="100 99 98"
build_list=("$build_string")
echo $build_list
for i in "${build_list[#]:1}"
do echo "i: " $i
done
The for loop does not print anything. Could you help me? Thanks.
I believe you are not converting the array properly (or at all).
Please see this snippet:
build_string="100 99 98"
#build_list=("$build_string") <-- this is not converting into array, following line is.
IFS=' ' read -r -a build_list <<< "$build_string"
echo $build_list
for i in "${build_list[#]:1}"
do echo "i: " $i
done
sleep 2
now the output is:
100
i: 99
i: 98
Which sounds reasonable. The 100 is printed when you ask echo $build_string.
Reference: split string into array in bash
As pointed out by prefire, the double quotes on the second line are preventing array conversion. This snippet also works:
build_string="100 99 98"
build_list=($build_string)
echo $build_list
for i in "${build_list[#]:1}"
do echo "i: " $i
done
sleep 2
Note: I've added a sleep 2 at the end, so I can see what is being printed.
Replace the second line with this:
build_list=($build_string)
build_list=("$build_string")
build_list array only have one item, so
${build_list[#]:1 is empty.
I'm a bit stuck with something. I have a for loop like this:
#!/bin/bash
for i in {10..15}
do
I want to obtain the last digit of the number, so if i is 12, I want to get 2. I'm having difficulties with the syntax though. I've read that I should convert it into a character array, but when I do something like:
j=${i[#]}
echo $j
I don't get 1 0 1 1 1 2 and so on...I get 10, 11, 12...How do I get the numbers to be split up so I can get the last one of i, when I don't always know how many digits will make up i (ex. it may be 1, or 10, or a 100, etc.)?
Trick is to treat $i like a string.
for i in {10..15}; do j="${i: -1}"; echo $j; done
Of course, you do not need to assign to a variable if you don't want to:
for i in {10..15}; do echo "${i: -1}"; done
This answer which uses GNU shell parameter expansion is the most sensible method, I guess.
However, you can also use the double parenthesis construct which allows C-style manipulation of variables in Bash.
for i in {10..15}
do
(( j = i % 10 )) # modulo 10 always gives the ones' digit
echo $j
done
This awk command could solve your problem:
awk '{print substr($0,length,1)}' test_file
I'm assuming that the numbers are saved in a file test_file
If you want to use for loop:
for i in `cat test_1`
do
echo $i |tail -c 2
done
I'm using data that is returned by another person's ksh93 script in the format of a print to the standard output. Depending on the flag I give it, their script gives me the information I need for my code. It comes out like a list separated by spaces, such that a run of the program has the format of:
"1 3 4 7 8"
"First Third Fourth Seventh Eighth"
For what I'm working on, I need to be able to match the entries of each output, so that I could make the information print in the following format:
1:First
3:Third
4:Fourth
7:Seventh
8:Eighth
I need to do more than just printing with the data, I just need to be able to access the pairs of information in each of the strings. Even though the actual contents of the strings can be any number of values, the two strings I get from running the other script will always be the same length.
I'm wondering if there exists a way to iterate over both at the same time, something along the lines of:
str_1=$(other_script -f)
str_2=$(other_script -i)
for a,b in ${str_1},${str_2} ; do
print "${a}:${b}"
done
This obviously isn't the right syntax, but I have been unable to find a way to make it work. Is there a way to iterate over both at the same time?
I know I could convert them to arrays first then iterate by numerical element, but I would like to save the time of converting them if there's a way to iterate over both simultaneously.
Why do you think it is not quick to convert the strings to arrays?
For example:
`#!/bin/ksh93
set -u
set -A line1
string1="1 3 4 7 8"
line1+=( ${string1} )
set -A line2
string2="First Third Fourth Seventh Eighth"
line2+=( ${string2})
typeset -i num_elem_line1=${#line1[#]}
typeset -i num_elem_line2=${#line2[#]}
typeset -i loop_counter=0
if (( num_elem_line1 == num_elem_line2 ))
then
while (( loop_counter < num_elem_line1 ))
do
print "${line1[${loop_counter}]}:${line2[${loop_counter}]}"
(( loop_counter += 1 ))
done
fi
`
As with the other comments, not sure why an array would be out of the question, especially if you plan on referencing the individual elements more than once later in your code.
A sample script that assumes you want to maintain your str_1/str_2 variables as strings; we'll load into arrays for referencing individual elements:
$ cat testme
#!/bin/ksh
str_1="1 3 4 7 8"
str_2="First Third Fourth Seventh Eighth"
str1=( ${str_1} )
str2=( ${str_2} )
# at this point matching array elements have the same index (0..4) ...
echo "++++++++++ str1[index]=element"
for i in "${!str1[#]}"
do
echo "str1[${i}]=${str1[${i}]}"
done
echo "++++++++++ str2[index]=element"
for i in "${!str1[#]}"
do
echo "str2[${i}]=${str2[${i}]}"
done
# since matching array elements have the same index, we just need
# to loop through one set of indexes to allow us to access matching
# array elements at the same time ...
echo "++++++++++ str1:str2"
for i in "${!str1[#]}"
do
echo ${str1[${i}]}:${str2[${i}]}
done
echo "++++++++++"
And a run of the script:
$ testme
++++++++++ str1[index]=element
str1[0]=1
str1[1]=3
str1[2]=4
str1[3]=7
str1[4]=8
++++++++++ str2[index]=element
str2[0]=First
str2[1]=Third
str2[2]=Fourth
str2[3]=Seventh
str2[4]=Eighth
++++++++++ str1:str2
1:First
3:Third
4:Fourth
7:Seventh
8:Eighth
++++++++++
I'm working with an existing script which was written a bit messily. Setting up a loop with all of the spaghetti code could make a bigger headache than I want to deal with in the near term. Maybe when I have more time I can clean it up but for now, I'm just looking for a simple fix.
The script deals with virtual disks on a xen server. It reads multipath output and asks if particular LUNs should be formatted in any way based on specific criteria. However, rather than taking that disk path and inserting it, already formatted, into a configuration file, it simply presents every line in the format
'phy:/dev/mapper/UUID,xvd?,w',
UUID, of course, is an actual UUID.
The script actually presents each of the found LUNs in this format expecting the user to copy and paste them into the config file replacing each ? with a letter in sequence. This is tedious at best.
There are several ways to increment a number in bash. Among others:
var=$((var+1))
((var+=1))
((var++))
Is there a way to do the same with characters which doesn't involve looping over the entire alphabet such that I could easily "increment" the disk assignment from xvda to xvdb, etc?
To do an "increment" on a letter, define the function:
incr() { LC_CTYPE=C printf "\\$(printf '%03o' "$(($(printf '%d' "'$1")+1))")"; }
Now, observe:
$ echo $(incr a)
b
$ echo $(incr b)
c
$ echo $(incr c)
d
Because, this increments up through ASCII, incr z becomes {.
How it works
The first step is to convert a letter to its ASCII numeric value. For example, a is 97:
$ printf '%d' "'a"
97
The next step is to increment that:
$ echo "$((97+1))"
98
Or:
$ echo "$(($(printf '%d' "'a")+1))"
98
The last step is convert the new incremented number back to a letter:
$ LC_CTYPE=C printf "\\$(printf '%03o' "98")"
b
Or:
$ LC_CTYPE=C printf "\\$(printf '%03o' "$(($(printf '%d' "'a")+1))")"
b
Alternative
With bash, we can define an associative array to hold the next character:
$ declare -A Incr; last=a; for next in {b..z}; do Incr[$last]=$next; last=$next; done; Incr[z]=a
Or, if you prefer code spread out over multiple lines:
declare -A Incr
last=a
for next in {b..z}
do
Incr[$last]=$next
last=$next
done
Incr[z]=a
With this array, characters can be incremented via:
$ echo "${Incr[a]}"
b
$ echo "${Incr[b]}"
c
$ echo "${Incr[c]}"
d
In this version, the increment of z loops back to a:
$ echo "${Incr[z]}"
a
How about an array with entries A-Z assigned to indexes 1-26?
IFS=':' read -r -a alpharray <<< ":A:B:C:D:E:F:G:H:I:J:K:L:M:N:O:P:Q:R:S:T:U:V:W:X:Y:Z"
This has 1=A, 2=B, etc. If you want 0=A, 1=B, and so on, remove the first colon.
IFS=':' read -r -a alpharray <<< "A:B:C:D:E:F:G:H:I:J:K:L:M:N:O:P:Q:R:S:T:U:V:W:X:Y:Z"
Then later, where you actually need the letter;
var=$((var+1))
'phy:/dev/mapper/UUID,xvd${alpharray[$var]},w',
The only problem is that if you end up running past 26 letters, you'll start getting blanks returned from the array.
Use a Bash 4 Range
You can use a Bash 4 feature that lets you specify a range within a sequence expression. For example:
for letter in {a..z}; do
echo "phy:/dev/mapper/UUID,xvd${letter},w"
done
See also Ranges in the Bash Wiki.
Here's a function that will return the next letter in the range a-z. An input of 'z' returns 'a'.
nextl(){
((num=(36#$(printf '%c' $1)-9) % 26+97));
printf '%b\n' '\x'$(printf "%x" $num);
}
It treats the first letter of the input as a base 36 integer, subtracts 9, and returns the character whose ordinal number is 'a' plus that value mod 26.
Use Jot
While the Bash range option uses built-ins, you can also use a utility like the BSD jot utility. This is available on macOS by default, but your mileage may vary on Linux systems. For example, you'll need to install athena-jot on Debian.
More Loops
One trick here is to pre-populate a Bash array and then use an index variable to grab your desired output from the array. For example:
letters=( "" $(jot -w %c 26 a) )
for idx in 1 26; do
echo ${letters[$idx]}
done
A Loop-Free Alternative
Note that you don't have to increment the counter in a loop. You can do it other ways, too. Consider the following, which will increment any letter passed to the function without having to prepopulate an array:
increment_var () {
local new_var=$(jot -nw %c 2 "$1" | tail -1)
if [[ "$new_var" == "{" ]]; then
echo "Error: You can't increment past 'z'" >&2
exit 1
fi
echo -n "$new_var"
}
var="c"
var=$(increment_var "$var")
echo "$var"
This is probably closer to what the OP wants, but it certainly seems more complex and less elegant than the original loop recommended elsewhere. However, your mileage may vary, and it's good to have options!
I'm trying to read from a file the data that it contains and get 2 important pieces of data from the file and use it in a bash script. A string and then a number for example:
Box 12
Toy 85
Dog 13
Bottle 22
I was thinking I could write a while loop to loop through the file and store the data into a variable. However I need two different variables, one for the number and one for the word. How do I get them separated into two variables?
Example code:
#!/bin/bash
declare -a textarr numarr
while read -r text num;do
textarr+=("$text")
numarr+=("$num")
done <file
echo ${textarr[1]} ${numarr[1]} #will print Toy 85
data are stored into two array variables: textarr numarr.
You can access each one of them using index ${textarr[$index]} or all of them at once with ${textarr[#]}
To read all the data into a single associative array (in bash 4.0 or newer):
#!/bin/bash
declare -A data=( )
while read -r key value; do
data[$key]=$value
done <file
With that done, you can retrieve a value by key efficiently:
echo "${data[Box]}"
...or iterate over all keys:
for key in "${!data[#]}"; do
value=${data[$key]}
echo "Key $key has value $value"
done
You'll note that read takes multiple names on its argument list. When given more than one argument, it splits fields by IFS, putting columns into their respective variables (with the entire rest of the line going into the last variable named, if more columns exist than variables are named).
Here I provide my own solution which should be discussed. I am not sure this is a good solution or not. Using while read construct has the drawback of starting a new shell and it will not be able to update a variable outside the loop. Here is an example code which you can modify to suite your own need. If you have more column data to use, then slight adjustment is need.
#!/bin/sh
res=$(awk 'BEGIN{OFS=" "}{print $2, $3 }' mytabularfile.tab)
n=0
for x in $res; do
row=$(expr $n / 2)
col=$(expr $n % 2)
#echo "row: $row column: $col value: $x"
if [ $col -eq 0 ]; then
if [ $n -gt 0 ]; then
echo "row: $row "
echo col1=$col1 col2=$col2
fi
col1=$x
else
col2=$x
fi
n=$(expr $n + 1)
done
row=$(expr $row + 1)
echo "last row: $row col1=$col1 col2=$col2"