Need to save content of nm function into variable. Files, which nm should run are arguments of script.
Currently I have:
while [ $i -le $#]
do
eval nm "\$$i"
i=$(( i+1 ))
done
which list me nm result of each file.
But I need to save result of nm file into variable.
I tried
eval CONTENT=$(nm "\$$i")
but this show me error "nm: '$1': No such file."
#devnull has solved your immediate problem (in his comment), but I suggest you rewrite your loop as follows:
for f
do
CONTENT=$(nm "$f")
# ... work with $CONTENT
done
A for loop without in ... implicitly loops over all arguments passed to the script.
Since f will then directly contain the value of each argument, there is no need to use eval.
(As an aside, your original code won't run as posted, because the [ ... ] conditional will break for 2 reasons: (a) $i is not initialized and (b) the closing ] must have a space before it.)
"eval" is part of the command you need to redirect:
CONTENT=$(eval nm "\$$i")
You will have to set up an array to store results tho:
CONTENT[$i]=$(eval nm "$\$$i")
Related
Assume there are several files like the following
CLIENT_1.csv
CLIENT_2.csv
CLIENT_3.csv
CLIENT_4.csv
Is there any shell command/awk that we can use to direct the 1,2,3,4 into a variable named "ID"? So that we can do the following
if [ ${ID} != 4 ]
then
blah blah blah
fi
To get the number part for each file:
for file in CLIENT_*.csv ; do
id=${file%.csv} # remove trailing '.csv'
id=${id#CLIENT_} # remove leading 'CLIENT_'
if [ "$id" != 4 ] ; then ... ; fi
done
This is pretty much a repeat of this question.
How to iterate over files in a directory with Bash?
It uses filename wildcarding to iterate through the list. In your case you would use:
for filename in /mydirectory/CLIENT_*.csv; do
#whatever you wanted to do
done
Here is another way to do it where the filename string pattern is a variable.
bash: filenames with wildcards in variables
The file names are stored in the variable file (looking at the accepted answer) after the wildcarding is expanded in the for loop initialization. Again using the power of wildcarding your example would look something like this:
putfile=CLIENT_*.csv
for file in $putfile; do #whatever you wanted to do
done
Would like to read multiple values from a property file using a shell script
My properties files looks something like below, the reason I added it following way was to make sure, if in future more students joins I just need to add in in the properties file without changing any thing in the shell script.
student.properties
total_student=6
student_name_1="aaaa"
student_name_2="bbbb"
student_name_3="cccc"
student_name_4="dddd"
student_name_5="eeee"
When I run below script I not getting the desired output, for reading the student names from properties file
student.sh
#!/bin/bash
. /student.properties
i=1
while [ $i -lt $total_student ]
do
{
std_Name=$student_name_$i
echo $std_Name
#****** my logic *******
} || {
echo "ERROR..."
}
i=`expr $i + 1`
done
Output is something like this
1
2
3
4
5
I understand the script is not getting anything for $student_name_ hence only $i value is getting printed.
Hence, wanted to know how to read values from the properties file.
You can do variable name interpolation with ${!foo}. If $foo is "bar", then ${!foo} gives you the value of $bar. In your code that means changing
std_Name=$student_name_$i
to
var=student_name_$i
std_Name=${!var}
Alternatively, you could store the names in an array. Then you wouldn't have to do any parsing.
student.properties
student_names=("aaaa" "bbbb" "cccc" "dddd" "eeee")
student.sh
#!/bin/bash
. /student.properties
for student_name in "${student_names[#]}"; do
...
done
You can use indirect expansion:
std_Name=student_name_$i
echo "${!std_Name}"
the expression ${!var} basically evaluates the variable twice:
first evaluation: student_name_1
second evaluation: foo
Note that this is rarely a good idea and that using an array is almost always preferred.
I want to run a shell script that can simultaneously loop through two variables.
So that I can have an input and output file name. I feel like this isn't too hard of a concept but any help is appreciated.
Files = "File1,
File2,
...
FileN
"
Output = OutFile1,
Outfile2,
...
OutfileN
"
and I would in theory my code would be:
for File in $Files
do
COMMAND --file $File --ouput $Output
done
Obviously, there needs to be another loop but I'm stuck, any help is appreciated.
You don't really need to loop 2 variables, just use 2 BASH arrays:
input=("File1" "File2" "File3")
output=("OutFile1" "OutFile2" "OutFile3")
for ((i=0; i<${#input[#]}; i++)); do
echo "Processing input=${input[$i]} and output=${output[$i]}"
done
zsh enables multiple loop variables before the list.
#!/bin/zsh
input2output=(
'File1' 'Outfile1'
'File2' 'Outfile2'
)
for input ouput in $input2output
do
echo "[$input] --> [$ouput]"
done
quotes from zsh(5.9) manual or man zshmisc
for name ... [ in word ... ] term do list done
More than one parameter name can appear before the list of words. If N names are given, then on each execution of the loop the next N words are assigned to the corresponding parameters. If there are more names than remaining words, the remaining parameters are each set to the empty string.
Regardless of the number of arguments passed to my script, I would like for the second to the last argument to always represent a specific variable in my code.
Executing the program I'd type something like this:
sh myprogram.sh -a arg_a -b arg_b special specific
test=("${3}")
echo $test
The results will show 'special'. So using that same idea if I try this (since I won't know that number of arguments):
secondToLastArg=$(($#-1))
echo $secondToLastArg
The results will show '3'. How do I dynamically assign the second to last argument?
You need a bit of math to get the number you want ($(($#-1))), then use indirection (${!n}) to get the actual argument.
$ set -- a b c
$ echo $#
a b c
$ n=$(($#-1))
$ echo $n
2
$ echo ${!n}
b
$
Indirection (${!n}) tells bash to use the value of n as the name of the variable to use ($2, in this case).
You can use $# as array & array chopping methods:
echo ${#:$(($#-1)):1}
It means, use 1 element starting from $(($#-1))...
If some old versions of shells do not support ${array:start:length} syntax but support only ${array:start} syntax, use below hack:
echo ${#:$(($#-1))} | { read x y ; echo $x; } # OR
read x unused <<< `echo ${#:$(($#-1))}`
After thoroughly searching for a way to create an associative array in bash, I found that declare -A array will do the trick. But the problem is, it is only for bash version 4 and the bash version the server has in our system is 3.2.16.
How can I achieve some sort of associative array-like hack in bash 3? The values will be passed to a script like
ARG=array[key];
./script.sh ${ARG}
EDIT: I know that I can do this in awk, or other tools but strict bash is needed for the scenario I am trying to solve.
Bash 3 has no associative arrays, so you're going to have to use some other language feature(s) for your purpose. Note that even under bash 4, the code you wrote doesn't do what you claim it does: ./script.sh ${ARG} does not pass the associative array to the child script, because ${ARG} expands to nothing when ARG is an associative array. You cannot pass an associative array to a child process, you need to encode it anyway.
You need to define some argument passing protocol between the parent script and the child script. A common one is to pass arguments in the form key=value. This assumes that the character = does not appear in keys.
You also need to figure out how to represent the associative array in the parent script and in the child script. They need not use the same representation.
A common method to represent an associative array is to use separate variables for each element, with a common naming prefix. This requires that the key name only consists of ASCII letters (of either case), digits and underscores. For example, instead of ${myarray[key]}, write ${myarray__key}. If the key is determined at run time, you need a round of expansion first: instead of ${myarray[$key]}, write
n=myarray__${key}; echo ${!n}
For an assignment, use printf -v. Note the %s format to printf to use the specified value. Do not write printf -v "myarray__${key}" %s "$value" since that would treat $value as a format and perform printf % expansion on it.
printf -v "myarray__${key}" %s "$value"
If you need to pass an associative array represented like this to a child process with the key=value argument representation, you can use ${!myarray__*} to enumerate over all the variables whose name begins with myarray__.
args=()
for k in ${!myarray__*}; do
n=$k
args+=("$k=${!n}")
done
In the child process, to convert arguments of the form key=value to separate variables with a prefix:
for x; do
if [[ $x != *=* ]]; then echo 1>&2 "KEY=VALUE expected, but got $x"; exit 120; fi
printf -v "myarray__${x%%=*}" %s "${x#*=}"
done
By the way, are you sure that this is what you need? Instead of calling a bash script from another bash script, you might want to run the child script in a subshell instead. That way it would inherit from all the variables of the parent.
Here is another post/explanation on associative arrays in bash 3 and older using parameter expansion:
https://stackoverflow.com/a/4444841
Gilles' method has a nice if statement to catch delimiter issues, sanitize oddball input ...etc. Use that.
If you are somewhat familiar with parameter expansion:
http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html
To use in your scenario [ as stated: sending to script ]:
Script 1:
sending_array.sh
# A pretend Python dictionary with bash 3
ARRAY=( "cow:moo"
"dinosaur:roar"
"bird:chirp"
"bash:rock" )
bash ./receive_arr.sh "${ARRAY[#]}"
Script 2: receive_arr.sh
argAry1=("$#")
function process_arr () {
declare -a hash=("${!1}")
for animal in "${hash[#]}"; do
echo "Key: ${animal%%:*}"
echo "Value: ${animal#*:}"
done
}
process_arr argAry1[#]
exit 0
Method 2, sourcing the second script:
Script 1:
sending_array.sh
source ./receive_arr.sh
# A pretend Python dictionary with bash 3
ARRAY=( "cow:moo"
"dinosaur:roar"
"bird:chirp"
"bash:rock" )
process_arr ARRAY[#]
Script 2: receive_arr.sh
function process_arr () {
declare -a hash=("${!1}")
for animal in "${hash[#]}"; do
echo "Key: ${animal%%:*}"
echo "Value: ${animal#*:}"
done
}
References:
Passing arrays as parameters in bash
If you don't want to handle a lot of variables, or keys are simply invalid variable identifiers, and your array is guaranteed to have less than 256 items, you can abuse function return values. This solution does not require any subshell as the value is readily available as a variable, nor any iteration so that performance screams. Also it's very readable, almost like the Bash 4 version.
Here's the most basic version:
hash_index() {
case $1 in
'foo') return 0;;
'bar') return 1;;
'baz') return 2;;
esac
}
hash_vals=("foo_val"
"bar_val"
"baz_val");
hash_index "foo"
echo ${hash_vals[$?]}
More details and variants in this answer
You can write the key-value pairs to a file and then grep by key. If you use a pattern like
key=value
then you can egrep for ^key= which makes this pretty safe.
To "overwrite" a value, just append the new value at the end of the file and use tail -1 to get just the last result of egrep
Alternatively, you can put this information into a normal array using key=value as value for the array and then iterator over the array to find the value.
This turns out to be ridiculously easy. I had to convert a bash 4 script that used a bunch of associative arrays to bash 3. These two helper functions did it all:
array_exp() {
exp=${#//[/__}
eval "${exp//]}"
}
array_clear() {
unset $(array_exp "echo \${!$1__*}")
}
I'm flabbergasted that this actually works, but that's the beauty of bash.
E.g.
((all[ping_lo] += counts[ping_lo]))
becomes
array_exp '((all[ping_lo] += counts[ping_lo]))'
Or this print statement:
printf "%3d" ${counts[ping_lo]} >> $return
becomes
array_exp 'printf "%3d" ${counts[ping_lo]}' >> $return
The only syntax that changes is clearing. This:
counts=()
becomes
array_clear counts
and you're set. You could easily tell array_exp to recognize expressions like "=()" and handle them by rewriting them as array_clear expressions, but I prefer the simplicity of the above two functions.