I have a problem with writing bash script. The problem is in comparison of strings. When I launch it, there's no errors. However in result, it is always changing the variable client.
So if for an example we have two lines in file
apple A
orange D
and if I give the who=A I expect to see in result apple, or if at D - orange
But no matter of what I choose A or D it is always giving me the result - orange
No matter of the strings, it always change the variable client, like ignoring the comparison. Please help.
while read line
do
IFS=" "
set -- $line
echo $2" "$who":"$1
if [[ "$2"="$who" ]]
then
echo "change"
client=$1
fi
done < $file
echo $client
So now I changed the code as in one of the comment below, but now the caparison always false therefore the variable client is always empty
while read -r line
do
#IFS=" "
#set -- $line
#echo $2" "$who":"$1
#if [[ "$2" = "$who" ]]
a="${line% *}"
l="${line#* }"
if [[ "$l" == "$who" ]]
then
echo "hi"
client="$a"
fi
done < $file
If you have data in a file with each line like apple D and you want to read the file and separate then items, the parameter expansion/substring extraction is the correct way to process the line. For example (note $who is taken from your problem statement):
while read -r line
do
fruit="${line% *}" # remove from end to space
letter="${line#* }" # remove from start to space
if [[ "$letter" == "$who" ]]
then
echo "change"
client="$fruit"
fi
done < $file
Short Example
Here is a quick example of splitting the words with parameter expansion/substring extraction:
#!/bin/bash
while read -r line
do
fruit="${line% *}"
letter="${line#* }"
echo "fruit: $fruit letter: $letter"
done
exit 0
input
$ cat dat/apple.txt
Apple A
Orange D
output
$ bash apple.sh <dat/apple.txt
fruit: Apple letter: A
fruit: Orange letter: D
Change if [[ "$2"="$who" ]] to
if [[ "$2" = "$who" ]]
spaces around =
Example (for clarification):
who=A
while read line
do
IFS=" "
set -- $line
echo $2" "$who":"$1
if [[ "$2" = "$who" ]]
then
echo "change"
client=$1
fi
done < file #this is the file I used for testing
echo $client
Output:
A A:apple
change
D A:orange
apple
For who=D:
A D:apple
D D:orange
change
orange
You do need spaces around that = operator.
However, I think you're facing yet another issue as you're trying to change the value of the client variable from inside the while loop (which executes in a subshell). I don't think that will work; see this quesion for details.
Related
Here is my code
vmname="$1"
EXCEPTLIST="desktop-01|desktop-02|desktop-03|desktop-04"
if [[ $vmname != #(${EXCEPTLIST}) ]]; then
echo "${vmname}"
else
echo "Its in the exceptlist"
fi
The above code works perfectly but my question is , the EXCEPTLIST can be a long line, say 100 server names. In that case its hard to put all that names in one line. In that situation is there any way to make the variable EXCEPTLIST to be a multiline variable ? something like as follows:
EXCEPTLIST="desktop-01|desktop-02|desktop-03| \n
desktop-04|desktop-05|desktop-06| \n
desktop-07|desktop-08"
I am not sure but was thinking of possibilities.
Apparently I would like to know the terminology of using #(${})- Is this called variable expansion or what ? Does anyone know the documentation/explain to me about how this works in bash. ?
One can declare an array if the data/string is long/large. Use IFS and printf for the format string, something like:
#!/usr/bin/env bash
exceptlist=(
desktop-01
desktop-02
desktop-03
desktop-04
desktop-05
desktop-06
)
pattern=$(IFS='|'; printf '#(%s)' "${exceptlist[*]}")
[[ "$vmname" != $pattern ]] && echo good
In that situation is there any way to make the variable EXCEPTLIST to be a multiline variable ?
With your given input/data an array is also a best option, something like:
exceptlist=(
'desktop-01|desktop-02|desktop-03'
'desktop-04|desktop-05|desktop-06'
'desktop-07|desktop-08'
)
Check what is the value of $pattern variable one way is:
declare -p pattern
Output:
declare -- pattern="#(desktop-01|desktop-02|desktop-03|desktop-04|desktop-05|desktop-06)"
Need to test/check if $vmname is an empty string too, since it will always be true.
On a side note, don't use all upper case variables for purely internal purposes.
The $(...) is called Command Substitution.
See LESS=+'/\ *Command Substitution' man bash
In addition to what was mentioned in the comments about pattern matching
See LESS=+/'(pattern-list)' man bash
See LESS=+/' *\[\[ expression' man bash
s there any way to make the variable EXCEPTLIST to be a multiline variable ?
I see no reason to use matching. Use a bash array and just compare.
exceptlist=(
desktop-01
desktop-02
desktop-03
desktop-04
desktop-05
desktop-06
)
is_in_list() {
local i
for i in "${#:2}"; do
if [[ "$1" = "$i" ]]; then
return 0
fi
done
return 1
}
if is_in_list "$vmname" "${EXCEPTLIST[#]}"; then
echo "is in exception list ${vmname}"
fi
#(${})- Is this called variable expansion or what ? Does anyone know the documentation/explain to me about how this works in bash. ?
${var} is a variable expansion.
#(...) are just characters # ( ).
From man bash in Compund commands:
[[ expression ]]
When the == and != operators are used, the string to the right of the operator is considered a pattern and matched according to the rules
described below under Pattern Matching, as if the extglob shell option were enabled. ...
From Pattern Matching in man bash:
#(pattern-list)
Matches one of the given patterns
[[ command receives the #(a|b|c) string and then matches the arguments.
There is absolutely no need to use Bash specific regex or arrays and loop for a match, if using grep for raw string on word boundary.
The exception list can be multi-line, it will work as well:
#!/usr/bin/sh
exceptlist='
desktop-01|desktop-02|desktop-03|
deskop-04|desktop-05|desktop-06|
desktop-07|deskop-08'
if printf %s "$exceptlist" | grep -qwF "$1"; then
printf '%s is in the exceptlist\n' "$1"
fi
I wouldn't bother with multiple lines of text. This is would be just fine:
EXCEPTLIST='desktop-01|desktop-02|desktop-03|'
EXCEPTLIST+='desktop-04|desktop-05|desktop-06|'
EXCEPTLIST+='desktop-07|desktop-08'
The #(...) construct is called extended globbing pattern and what it does is an extension of what you probably already know -- wildcards:
VAR='foobar'
if [[ "$VAR" == fo?b* ]]; then
echo "Yes!"
else
echo "No!"
fi
A quick walkthrough on extended globbing examples: https://www.linuxjournal.com/content/bash-extended-globbing
#!/bin/bash
set +o posix
shopt -s extglob
vmname=$1
EXCEPTLIST=(
desktop-01 desktop-02 desktop-03
...
)
if IFS='|' eval '[[ ${vmname} == #(${EXCEPTLIST[*]}) ]]'; then
...
Here's one way to load a multiline string into a variable:
fn() {
cat <<EOF
desktop-01|desktop-02|desktop-03|
desktop-04|desktop-05|desktop-06|
desktop-07|desktop-08
EOF
}
exceptlist="$(fn)"
echo $exceptlist
As to solving your specific problem, I can think of a variety of approaches.
Solution 1, since all the desktop has the same desktop-0 prefix and only differ in the last letter, we can make use of {,} or {..} expansion as follows:
vmname="$1"
found=0
for d in desktop-{01..08}
do
if [[ "$vmname" == $d ]]; then
echo "It's in the exceptlist"
found=1
break
fi
done
if (( !found )); then
echo "Not found"
fi
Solution 2, sometimes, it is good to provide a list in a maintainable clear text list. We can use a while loop and iterate through the list
vmname="$1"
found=0
while IFS= read -r d
do
if [[ "$vmname" == $d ]]; then
echo "It's in the exceptlist"
found=1
break
fi
done <<EOF
desktop-01
desktop-02
desktop-03
desktop-04
desktop-05
desktop-06
desktop-07
desktop-08
EOF
if (( !found )); then
echo "Not found"
fi
Solution 3, we can desktop the servers using regular expressions:
vmname="$1"
if [[ "$vmname" =~ ^desktop-0[1-8]$ ]]; then
echo "It's in the exceptlist"
else
echo "Not found"
fi
Solution 4, we populate an array, then iterate through an array:
vmname="$1"
exceptlist=()
exceptlist+=(desktop-01 desktop-02 desktop-03 deskop-04)
exceptlist+=(desktop-05 desktop-06 desktop-07 deskop-08)
found=0
for d in ${exceptlist[#]}
do
if [[ "$vmname" == "$d" ]]; then
echo "It's in the exceptlist"
found=1
break;
fi
done
if (( !found )); then
echo "Not found"
fi
Sometimes I need to find a specific serial in a box with many items, so I wrote a simple Bash script that allows me to use a barcode scanner to scan hundreds of barcodes until a match is found, at which point the screen flashes (so I can see it from the corner of my eyes while looking at the box).
The script works great, but it only checks against one specific serial number provided by the user. Here's the code:
#!/bin/bash
INPUT=''
SCAN=''
SN=''
I='0'
clear
printf "Enter serial\n"
read INPUT
SN=`printf "${INPUT}" | tr '[:lower:]' '[:upper:]'`
# Keep comparing scans to needed serial until a match is found
while [[ "${SCAN}" != *"${SN}"* ]];
do
clear
printf "Looking for [ "${SN}" ]\n"
printf "Please scan barcode\n"
read INPUT
SCAN=`printf "${INPUT}" | tr '[:lower:]' '[:upper:]'`
done
# Flash screen when match is found
while [[ "${I}" -lt 3 ]];
do
printf '\e[?5h' && sleep 0.3
printf '\e[?5l' && sleep 0.3
I=$[${I}+1]
done
printf "FOUND\n"
Today I spent hours trying to implement a way to pass multiple possible serial numbers as command line arguments, but I can't seem to get it working. I would like to be able to pass a small, manageable number of possible serials, like this:
$ ./script.sh sn1 sn2 sn3 sn4 sn5
And for the script continue asking for input until I come across the item I am looking for.
I've studied the handling of shell arguments, but I can't seem to "massage" the above while loop to get it to check if the scanned serial exists in the array (created from the command line arguments passed):
#!/bin/bash
snList=( "$#" )
INPUT=''
SCAN=''
SN=''
I='0'
clear
#displaying "things" so I can see what each variable contains (debugging)
printf "$#\n"
printf "$0\n"
printf "$*\n"
printf "$0\n"
printf "$1\n"
printf "$2\n"
printf "$3\n"
printf "snList: $snList\n"
printf "snList[#]: ${snList[#]}\n"
printf "snList[*]: ${snList[*]}\n"
# Keep comparing scans to needed serial until a match is found
while [[ ! " ${snList[*]} " =~ "${SCAN}" ]];
do
clear
printf "Looking for [ "$*" ]\n"
printf "Please scan barcode\n"
read INPUT
SCAN=`printf "${INPUT}" | tr '[:lower:]' '[:upper:]'`
done
I've tried using ${snList[#]} in the loop as well, same result, it behaves like a match was found immediately, without even asking for a scan (indicating that the content of the while loop is not being executed).
Any help will be immensely appreciated, I think I am close, but I can't figure out what I am doing wrong.
Thanks in advance!
Something like this maybe?
#!/usr/bin/env bash
to_compare_input=("$#")
exglob_pattern_input=$(IFS='|'; printf '%s' "#(${to_compare_input[*]})")
until [[ $user_input == $exglob_pattern_input ]]; do
read -r user_input
done
Run the script with the the following arguments.
bash -x ./myscript foo bar baz more
Output
+ to_compare_input=("$#")
++ IFS='|'
++ printf %s '#(foo|bar|baz|more)'
+ exglob_pattern_input='#(foo|bar|baz|more)'
+ [[ '' == #(foo|bar|baz|more) ]]
+ read -r user_input
papa
+ [[ papa == #(foo|bar|baz|more) ]]
+ read -r user_input
mama
+ [[ mama == #(foo|bar|baz|more) ]]
+ read -r user_input
baz
+ [[ baz == #(foo|bar|baz|more) ]]
The first user input is empty since the builtinread has not been executed to ask for the user's input. As shown at the debug message.
+ [[ '' == #(foo|bar|baz|more) ]]
The second (assuming the user has entered papa) is papa
The third (assuming the user has entered mama) is mama
The last is baz which breaks out of off the until loop, because it belongs to the $extglob_pattern_input, which is an extglob feature.
A regex is also an alternative using the =~ operator.
#!/usr/bin/env bash
to_compare_input=("$#")
regex_pattern_input=$(IFS='|'; printf '%s' "^(${to_compare_input[*]})$")
until [[ $user_input =~ $regex_pattern_input ]]; do
read -r user_input
done
Run the script same as before.
Using two loops which was suggested in the comments section.
#!/usr/bin/env bash
to_compare_input=("$#")
inarray() {
local n=$1 h
shift
for h; do
[[ $n == "$h" ]] && return
done
return 1
}
until inarray "$user_input" "${to_compare_input[#]}"; do
read -r user_input
done
As for the tr if your version of bash supports the ^^ and ,, for uppercase and lowercase parameter expansion. use ${user_input^^}
until [[ ${user_input^^} == $exglob_pattern_input ]]; do
until [[ ${user_input^^} =~ $regex_pattern_input ]]; do
until inarray "${user_input^^}" "${to_compare_input[#]}"; do
Assuming no spaces in the bar code texts. You can do something like this
while read -r INPUT
do
#Append spaces to prevent substring matching
if [[ $(echo " $# " | grep -i " ${INPUT} " | wc -l) -eq 1 ]]
then
break
fi
done
I'm trying to get the first character of a variable, but I'm getting a Bad substitution error. Can anyone help me fix it?
code is:
while IFS=$'\n' read line
do
if [ ! ${line:0:1} == "#"] # Error on this line
then
eval echo "$line"
eval createSymlink $line
fi
done < /some/file.txt
Am I doing something wrong or is there a better way of doing this?
-- EDIT --
As requested - here's some sample input which is stored in /some/file.txt
$MOZ_HOME/mobile/android/chrome/content/browser.js
$MOZ_HOME/mobile/android/locales/en-US/chrome/browser.properties
$MOZ_HOME/mobile/android/components/ContentPermissionPrompt.js
To get the first character of a variable you need to say:
v="hello"
$ echo "${v:0:1}"
h
However, your code has a syntax error:
[ ! ${line:0:1} == "#"]
# ^-- missing space
So this can do the trick:
$ a="123456"
$ [ ! "${a:0:1}" == "#" ] && echo "doesnt start with #"
doesnt start with #
$ a="#123456"
$ [ ! "${a:0:1}" == "#" ] && echo "doesnt start with #"
$
Also it can be done like this:
$ a="#123456"
$ [ "$(expr substr $a 1 1)" != "#" ] && echo "does not start with #"
$
$ a="123456"
$ [ "$(expr substr $a 1 1)" != "#" ] && echo "does not start with #"
does not start with #
Update
Based on your update, this works to me:
while IFS=$'\n' read line
do
echo $line
if [ ! "${line:0:1}" == "#" ] # Error on this line
then
eval echo "$line"
eval createSymlink $line
fi
done < file
Adding the missing space (as suggested in fedorqui's answer ;) ) works for me.
An alternative method/syntax
Here's what I would do in Bash if I want to check the first character of a string
if [[ $line != "#"* ]]
On the right hand side of ==, the quoted part is treated literally whereas * is a wildcard for any sequence of character.
For more information, see the last part of Conditional Constructs of Bash reference manual:
When the ‘==’ and ‘!=’ operators are used, the string to the right of the operator is considered a pattern and matched according to the rules described below in Pattern Matching
Checking that you're using the right shell
If you are getting errors such as "Bad substitution error" and "[[: not found" (see comment) even though your syntax is fine (and works fine for others), it might indicate that you are using the wrong shell (i.e. not Bash).
So to make sure you are using Bash to run the script, either
make the script executable and use an appropriate shebang e.g. #!/bin/bash
or execute it via bash my_script
Also note that sh is not necessarily bash, sometimes it can be dash (e.g. in Ubuntu) or just plain ol' Bourne shell.
Try this:
while IFS=$'\n' read line
do
if ! [ "${line:0:1}" = "#" ]; then
eval echo "$line"
eval createSymlink $line
fi
done < /some/file.txt
or you can use the following for your if syntax:
if [[ ! ${line:0:1} == "#" ]]; then
TIMTOWTDI ^^
while IFS='' read -r line
do
case "${line}" in
"#"*) echo "${line}"
;;
*) createSymlink ${line}
;;
esac
done < /some/file.txt
Note: I dropped the eval, which could be needed in some (rare!) cases (and are dangerous usually).
Note2: I added a "safer" IFS & read (-r, raw) but you can revert to your own if it is better suited. Note that it still reads line by line.
Note3: I took the habit of using always ${var} instead of $var ... works for me (easy to find out vars in complex text, and easy to see where they begin and end at all times) but not necessary here.
Note4: you can also change the test to : *"#"*) if some of the (comments?) lines can have spaces or tabs before the '#' (and none of the symlink lines does contain a '#')
I'm attempting to read a config file that is formatted as follows:
USER = username
TARGET = arrows
I realize that if I got rid of the spaces, I could simply source the config file, but for security reasons I'm trying to avoid that. I know there is a way to read the config file line by line. I think the process is something like:
Read lines into an array
Filter out all of the lines that start with #
search for the variable names in the array
After that I'm lost. Any and all help would be greatly appreciated. I've tried something like this with no success:
backup2.config>cat ~/1
grep '^[^#].*' | while read one two;do
echo $two
done
I pulled that from a forum post I found, just not sure how to modify it to fit my needs since I'm so new to shell scripting.
http://www.linuxquestions.org/questions/programming-9/bash-shell-program-read-a-configuration-file-276852/
Would it be possible to automatically assign a variable by looping through both arrays?
for (( i = 0 ; i < ${#VALUE[#]} ; i++ ))
do
"${NAME[i]}"=VALUE[i]
done
echo $USER
Such that calling $USER would output "username"? The above code isn't working but I know the solution is something similar to that.
The following script iterates over each line in your input file (vars in my case) and does a pattern match against =. If the equal sign is found it will use Parameter Expansion to parse out the variable name from the value. It then stores each part in it's own array, name and value respectively.
#!/bin/bash
i=0
while read line; do
if [[ "$line" =~ ^[^#]*= ]]; then
name[i]=${line%% =*}
value[i]=${line#*= }
((i++))
fi
done < vars
echo "total array elements: ${#name[#]}"
echo "name[0]: ${name[0]}"
echo "value[0]: ${value[0]}"
echo "name[1]: ${name[1]}"
echo "value[1]: ${value[1]}"
echo "name array: ${name[#]}"
echo "value array: ${value[#]}"
Input
$ cat vars
sdf
USER = username
TARGET = arrows
asdf
as23
Output
$ ./varscript
total array elements: 2
name[0]: USER
value[0]: username
name[1]: TARGET
value[1]: arrows
name array: USER TARGET
value array: username arrows
First, USER is a shell environment variable, so it might be better if you used something else. Using lowercase or mixed case variable names is a way to avoid name collisions.
#!/bin/bash
configfile="/path/to/file"
shopt -s extglob
while IFS='= ' read lhs rhs
do
if [[ $lhs != *( )#* ]]
then
# you can test for variables to accept or other conditions here
declare $lhs=$rhs
fi
done < "$configfile"
This sets the vars in your file to the value associated with it.
echo "Username: $USER, Target: $TARGET"
would output
Username: username, Target: arrows
Another way to do this using keys and values is with an associative array:
Add this line before the while loop:
declare -A settings
Remove the declare line inside the while loop and replace it with:
settings[$lhs]=$rhs
Then:
# set keys
user=USER
target=TARGET
# access values
echo "Username: ${settings[$user]}, Target: ${settings[$target]}"
would output
Username: username, Target: arrows
I have a script which only takes a very limited number of settings, and processes them one at a time, so I've adapted SiegeX's answer to whitelist the settings I care about and act on them as it comes to them.
I've also removed the requirement for spaces around the = in favour of ignoring any that exist using the trim function from another answer.
function trim()
{
local var=$1;
var="${var#"${var%%[![:space:]]*}"}"; # remove leading whitespace characters
var="${var%"${var##*[![:space:]]}"}"; # remove trailing whitespace characters
echo -n "$var";
}
while read line; do
if [[ "$line" =~ ^[^#]*= ]]; then
setting_name=$(trim "${line%%=*}");
setting_value=$(trim "${line#*=}");
case "$setting_name" in
max_foos)
prune_foos $setting_value;
;;
max_bars)
prune_bars $setting_value;
;;
*)
echo "Unrecognised setting: $setting_name";
;;
esac;
fi
done <"$config_file";
Thanks SiegeX. I think the later updates you mentioned does not reflect in this URL.
I had to edit the regex to remove the quotes to get it working. With quotes, array returned is empty.
i=0
while read line; do
if [[ "$line" =~ ^[^#]*= ]]; then
name[i]=${line%% =*}
value[i]=${line##*= }
((i++))
fi
done < vars
A still better version is .
i=0
while read line; do
if [[ "$line" =~ ^[^#]*= ]]; then
name[i]=`echo $line | cut -d'=' -f 1`
value[i]=`echo $line | cut -d'=' -f 2`
((i++))
fi
done < vars
The first version is seen to have issues if there is no space before and after "=" in the config file. Also if the value is missing, i see that the name and value are populated as same. The second version does not have any of these. In addition it trims out unwanted leading and trailing spaces.
This version reads values that can have = within it. Earlier version splits at first occurance of =.
i=0
while read line; do
if [[ "$line" =~ ^[^#]*= ]]; then
name[i]=`echo $line | cut -d'=' -f 1`
value[i]=`echo $line | cut -d'=' -f 2-`
((i++))
fi
done < vars
I am making a bash script where I want to find files that are equal to a variable. The equals will then be used.
I want to use "mogrify" to shrink a couple of image files that have the same name as the ones i gather from a list (similar to "dpkg -l"). It is not "dpkg -l" I am using but it is similar. My problem is that it prints all the files not just the equals. I am pretty sure this could be done with awk instead of a for-loop but I do not know how.
prog="`dpkg -l | awk '{print $1}'`"
for file in $dirone* $dirtwo*
do
if [ "basename ${file}" = "${prog}" ]; then
echo ${file} are equal
else
echo ${file} are not equal
fi
done
Could you please help me get this working?
First, I think there's a small typo. if [ "basename ${file}" =... should have backticks inside the double quotes, just like the prog=... line at the top does.
Second, if $prog is a multi-line string (like dpkg -l) you can't really compare a filename to the entire list. Instead you have to compare one item at a time to the filename.
Here's an example using dpkg and /usr/bin
#!/bin/bash
progs="`dpkg -l | awk '{print $2}'`"
for file in /usr/bin/*
do
base=`basename ${file}`
for prog in ${progs}
do
if [ "${base}" = "${prog}" ]; then
echo "${file}" matches "${prog}"
fi
done
done
The condition "$file = $prog" is a single string. You should try "$file" = "$prog" instead.
The following transcript shows the fix:
pax> ls -1 qq*
qq
qq.c
qq.cpp
pax> export xx=qq.cpp
pax> for file in qq* ; do
if [[ "${file} = ${xx}" ]] ; then
echo .....${file} equal
else
echo .....${file} not equal
fi
done
.....qq equal
.....qq.c equal
.....qq.cpp equal
pax> for file in qq* ; do
if [[ "${file}" = "${xx}" ]] ; then
echo .....${file} equal
else
echo .....${file} not equal
fi
done
.....qq not equal
.....qq.c not equal
.....qq.cpp equal
You can see in the last bit of output that only qq.cpp is shown as equal since it's the only one that matches ${xx}.
The reason you're getting true is because that's what non-empty strings will give you:
pax> if [[ "" ]] ; then
echo .....equal
fi
pax> if [[ "x" ]] ; then
echo .....equal
fi
.....equal
That's because that form is the string length checking variation. From the bash manpage under CONDITIONAL EXPRESSIONS:
string
-n string
True if the length of string is non-zero.
Update:
The new code in your question won't quite work as expected. You need:
if [[ "$(basename ${file})" = "${prog}" ]]; then
to actually execute basename and use its output as the first part of the equality check.
you can use case/esac
case "$file" in
"$prog" ) echo "same";;
esac