I am trying to create a variable based on $i
i=1
line="one two three four five six"
while [[ $i -lt 3 ]]; do
set string$i=`echo $line | cut -d" " -f1-3`
echo $string$i
do_stuff_here
done
when i do this I get the following output
1
the expected output is
one two three
In Fact when I echo $String1...i get the expected output...so its stored correctly.
I know its the way I am calling $string$1...but I have tried all kinds of quotes/parenthesis and Its not working. Can someone tell me how to call my variable?
Your while loop never stops unless you increment i in do_stuff_there, anyway, this should be closer to what you are expecting:
i=1
line="one two three four five six"
while [[ $i -lt 3 ]]; do
eval string$i=\"`echo $line | cut -d" " -f1-3`\"
eval echo \$string$i
do_stuff_here
done
Related
I have a following list.txt file with the content
cat list.txt
one
two
zero
three
four
I have a shell script (check.sh) like below,
for i in $(cat list.txt)
do
if [ $i != zero ]; then
echo "the number is $i"
else
exit 1
fi
done
it gives output like below,
./check.sh
the number is one
the number is two
I want to have script which continue with the rest of the items in the list.txt, but it should not process zero and continue with the rest of item.
eg.
the number is one
the number is two
the number is three
the number is four
I tried using "return" but it did not work, gave error.
./check.sh: line 6: return: can only `return' from a function or sourced script
About exit (and return)
The command exit will quit running script. There is no way to continue.
As well, return command will quit function. There in no more way to continue.
About reading input file
For processing line based input file, you'd better to use while read instead of for i in $(cat...:
Simply try:
while read -r i;do
if [ "$i" != "zero" ] ;then
echo number $i
fi
done <list.txt
Alternatively, you could drop unwanted entries before loop:
while read -r i;do
echo number $i
done < <( grep -v ^zero$ <list.txt)
Note: In this specific case, ^zero$ don't need to be quoted. Consider quoting if your string do contain special characters or spaces.
If you have more than one entries to drop, you could use
while read -r i;do echo number $i ;done < <(grep -v '^\(zero\|null\)$' <list.txt)
Alternatively, once input file filtered, use xargs:
If your process is only one single command, you could avoid bash loop by using xargs:
xargs -n 1 echo number < <(grep -v '^\(zero\|null\)$' <list.txt)
How to use continue in bash script
Maybe you are thinking about something like:
while read -r i;do
if [ "$i" = "zero" ] ;then
continue
fi
echo number $i
done <list.txt
Argument of continue is a number representing number of loop to shortcut.
Try this:
for i in {1..5};do
for l in {a..d};do
if [ "$i" -eq 3 ] && [ "$l" = "b" ] ;then
continue 2
fi
echo $i.$l
done
done
(This print 3.a and stop 3 serie at 3.b, breaking 2 loop level)
Then compare with
for i in {1..5};do
for l in {a..d};do
if [ "$i" -eq 3 ] && [ "$l" = "b" ] ;then
continue 1
fi
echo $i.$l
done
done
(This print 3.a , 3.c and 3.d. Only 3.b are skipped, breaking only 1 loop level)
I need to accept input from user (i.e. 'read').
This input can be either a single positive number or a range of numbers (in the form X-Y ).
I then need to validate this input and perform an iterative loop through the range of numbers (or just once in the case of only X).
examples:
1) User supplies: "8" or "8-"
Loop runs only a single time supplying the number 8
2) User supplies: "13-22"
Loop runs 11 times (13 through 22) referencing the number 13.
3) User supplies: "22-13"
Probably should behave like #2 above...but I'm open to other clean ways to validate the input.
I have worked on the following so far, which isn't very clean, complete, or even 100% correct for what I was asking - but it shows the effort and idea I'm going for:
echo "line?"; read -r deleteline
case "$deleteline" in
''|*[!0-9\-]*) echo "not a number";;
[1-9]|[1-9][0-9]*);;
esac
deleteline_lb=$(echo $deleteline|awk -F "-" '{print $1}')
deleteline_ub=$(echo $deleteline|awk -F "-" '{print $2}')
if [ ! $deleteline_lb = "" ] && [ ! "$deleteline_ub" = "" ]; then
delete_line_count=1
delete_line_count=$(expr $deleteline_ub - $deleteline_lb)
if [ $delete_line_count -le 0 ]; then
delete_line_count=1
fi
fi
i=1; while [ $i -le $delete_line_count ]; do
echo $deleteline_lb $i
i=$(($i + 1))
done
This needs to run in sh, things like seq are not supported - so stick with posix compliant methods...
To clarify I am looking to do the following (pseudo-code):
1) accept input from user
2) validate if input is in the form "#" or "#-#" (range).
3) Execute chosen (arbitrary) code path based on proper/improper input.
4) If single # is given then store that to variable to perform future operations against.
5) If range is given, store both numbers in variable to be able to perform the operation against the lower # up to the higher number. More specifically it would be "(higher #) - (lower #) + 1". So if range were 12-17 then we need to perform operation against 12, 6x. (17 - 12 + 1). IOW, 12-17 inclusive.
6) A way to easily denote if data set is range vs single number is also desired so that code path to each can be easily branched.
thanks for helping!
UPDATE:
Using my basic code I reworked it (with a bit of input from a friend), and basically came up with this:
while true;do
printf "\\delete lines? [e=Exit] ";read -r deleteline
case "$deleteline" in
[Ee]) break;;
*)
echo "$deleteline" | egrep -q '^[[:digit:]-]*$'
if [ $? -ne 0 ]; then
printf "\\n input is not a number.\\n"
else
delete_range_start=`echo $deleteline|awk -F "-" '{print $1}'`
delete_range_end=`echo $deleteline|awk -F "-" '{print $2}'`
if [ $delete_range_end -lt $delete_range_start ]; then
printf "\\n upper range must be higher than lower range.\\n"
else
if [ "$delete_range_end" = "" ]; then
delete_range_end=$delete_range_start
elif [ $delete_range_end -gt $lineNumbers ]; then
printf "\\Setting range to last entry\\n"
fi
break
fi
fi
;;
esac
done
deleteline=$delete_range_start
deleteloop=`expr $delete_range_end - $delete_range_start + 1`
i=1
while [ $i -le $deleteloop ]; do
# Insert all processing code in here
i=`expr $i + 1`
done
If you have a posix compliant awk, try this:
echo "$userInput" | awk -F- '
($1+0==$1&&$2+0==$2){
for(i=$1;($1<$2?i<=$2:i>=$2);)
print ($1<$2?i++:i--);
next
}
$1+0==$1{
print $1;
next
}
$2+0==$2{
print $2;
next
}
($1+0!=$1&&$2+0!=$2){
exit 1
}'
The script check if the 2 fields (separated with -) are numbers. If so, it prints these numbers in an ascending or descending way depending if the first number is greater or lower than the second one.
If only one input, the script just prints it.
If none of the field are number, it exits with a non zero value.
This script could be the validation step of a shell script like this:
$ cat test.sh
#!/bin/sh
echo -n "range: "
read -r range
validated_input=$(echo "$range" | awk -F- '($1+0==$1&&$2+0==$2){for(i=$1;($1<$2?i<=$2:i>=$2);)print ($1<$2?i++:i--);next}$1+0==$1{print $1;next}$2+0==$2{print $2;next}($1+0!=$1&&$2+0!=$2){exit 1}')
if [ $? -ne 0 ]; then
echo "Incorrect range" >&2
fi
for i in $validated_input; do
echo "$i"
done
Examples:
$ ./test.sh
range: 10-6
10
9
8
7
6
$ ./test.sh
range: 8-
8
$ ./test.sh
range: hello
Incorrect range
I have issue with an if statement. In WEDI_RC is saved log file in the following format:
name_of_file date number_of_starts
I want to compare first argument $1 with first column and if it is true than increment number of starts. When I start my script it works but just with one file, eg:
file1.c 11:23:07 1
file1.c 11:23:14 2
file1.c 11:23:17 3
file1.c 11:23:22 4
file2.c 11:23:28 1
file2.c 11:23:35 2
file2.c 11:24:10 3
file2.c 11:24:40 4
file2.c 11:24:53 5
file1.c 11:25:13 1
file1.c 11:25:49 2
file2.c 11:26:01 1
file2.c 11:28:12 2
Every time when I change file it begin counts from 1. I need to continue with counting when it ends.
Hope you understand me.
while read -r line
do
echo "line:"
echo $line
if [ "$1"="$($line | grep ^$1)" ]; then
number=$(echo $line | grep $1 | awk -F'[ ]' '{print $3}')
else
echo "error"
fi
done < $WEDI_RC
echo "file"
((number++))
echo $1 `date +"%T"` $number >> $WEDI_RC
There are at least two ways to resolve the problem. The most succinct is probably:
echo "$1 $(date +"%T") $(($(grep -c "^$1 " "$WEDI_RC") + 1))" >> "$WEDI_RC"
However, if you want to have counts for each file separately, you can do that using an associative array, assuming you have Bash version 4.x (not 3.x as is provided on Mac OS X, for example). This code assumes the file is correctly formatted (so that the counts do not reset to 1 each time the file name changes).
declare -A files # Associative array
while read -r file time count # Split line into three variables
do
echo "line: $file $time $count" # One echo - not two
files[$file]="$count" # Record the current maximum for file
done < "$WEDI_RC"
echo "$1 $(date +"%T") $(( ${files[$1]} + 1 ))" >> "$WEDI_RC"
The code uses read to split the line into three separate variables. It echoes what it read and records the current count. When the loop's done, it echoes the data to append to the file. If the file is new (not mentioned in the file yet), then you will get a 1 added.
If you need to deal with the broken file as input, then you can amend the code to count the number of entries for a file, instead of trusting the count value. The bare-array reference notation used in the (( … )) operation is necessary when incrementing the variable; you can't use ${array[sub]}++ with the increment (or decrement) operator because that evaluates to the value of the array element, not its name!
declare -A files # Associative array
while read -r file time count # Split line into three variables
do
echo "line: $file $time $count" # One echo - not two
((files[$file]++)) # Count the occurrences of file
done < "$WEDI_RC"
echo "$1 $(date +"%T") $(( ${files[$1]} + 1 ))" >> "$WEDI_RC"
You can even detect whether the format is in the broken or fixed style:
declare -A files # Associative array
while read -r file time count # Split line into three variables
do
echo "line: $file $time $count" # One echo - not two
if [ $((files[$file]++)) != "$count" ]
then echo "$0: warning - count out of sync: ${files[$file]} vs $count" >&2
fi
done < "$WEDI_RC"
echo "$1 $(date +"%T") $(( ${files[$1]} + 1 ))" >> "$WEDI_RC"
I don't get exactly what you want to achieve with your test [ "$1"="$($line | grep ^$1)" ] but it seems you are checking that the line start with the first argument.
If it is so, I think you can either:
provide the -o option to grep so that it print just the matched output (so $1)
use [[ "$line" =~ ^"$1" ]] as test.
I'm trying to write a small script that will count entries in a log file, and I'm incrementing a variable (USCOUNTER) which I'm trying to use after the loop is done.
But at that moment USCOUNTER looks to be 0 instead of the actual value. Any idea what I'm doing wrong? Thanks!
FILE=$1
tail -n10 mylog > $FILE
USCOUNTER=0
cat $FILE | while read line; do
country=$(echo "$line" | cut -d' ' -f1)
if [ "US" = "$country" ]; then
USCOUNTER=`expr $USCOUNTER + 1`
echo "US counter $USCOUNTER"
fi
done
echo "final $USCOUNTER"
It outputs:
US counter 1
US counter 2
US counter 3
..
final 0
You are using USCOUNTER in a subshell, that's why the variable is not showing in the main shell.
Instead of cat FILE | while ..., do just a while ... done < $FILE. This way, you avoid the common problem of I set variables in a loop that's in a pipeline. Why do they disappear after the loop terminates? Or, why can't I pipe data to read?:
while read country _; do
if [ "US" = "$country" ]; then
USCOUNTER=$(expr $USCOUNTER + 1)
echo "US counter $USCOUNTER"
fi
done < "$FILE"
Note I also replaced the `` expression with a $().
I also replaced while read line; do country=$(echo "$line" | cut -d' ' -f1) with while read country _. This allows you to say while read var1 var2 ... varN where var1 contains the first word in the line, $var2 and so on, until $varN containing the remaining content.
Always use -r with read.
There is no need to use cut, you can stick with pure bash solutions.
In this case passing read a 2nd var (_) to catch the additional "fields"
Prefer [[ ]] over [ ].
Use arithmetic expressions.
Do not forget to quote variables! Link includes other pitfalls as well
while read -r country _; do
if [[ $country = 'US' ]]; then
((USCOUNTER++))
echo "US counter $USCOUNTER"
fi
done < "$FILE"
minimalist
counter=0
((counter++))
echo $counter
You're getting final 0 because your while loop is being executed in a sub (shell) process and any changes made there are not reflected in the current (parent) shell.
Correct script:
while read -r country _; do
if [ "US" = "$country" ]; then
((USCOUNTER++))
echo "US counter $USCOUNTER"
fi
done < "$FILE"
I had the same $count variable in a while loop getting lost issue.
#fedorqui's answer (and a few others) are accurate answers to the actual question: the sub-shell is indeed the problem.
But it lead me to another issue: I wasn't piping a file content... but the output of a series of pipes & greps...
my erroring sample code:
count=0
cat /etc/hosts | head | while read line; do
((count++))
echo $count $line
done
echo $count
and my fix thanks to the help of this thread and the process substitution:
count=0
while IFS= read -r line; do
((count++))
echo "$count $line"
done < <(cat /etc/hosts | head)
echo "$count"
USCOUNTER=$(grep -c "^US " "$FILE")
Incrementing a variable can be done like that:
_my_counter=$[$_my_counter + 1]
Counting the number of occurrence of a pattern in a column can be done with grep
grep -cE "^([^ ]* ){2}US"
-c count
([^ ]* ) To detect a colonne
{2} the colonne number
US your pattern
Using the following 1 line command for changing many files name in linux using phrase specificity:
find -type f -name '*.jpg' | rename 's/holiday/honeymoon/'
For all files with the extension ".jpg", if they contain the string "holiday", replace it with "honeymoon". For instance, this command would rename the file "ourholiday001.jpg" to "ourhoneymoon001.jpg".
This example also illustrates how to use the find command to send a list of files (-type f) with the extension .jpg (-name '*.jpg') to rename via a pipe (|). rename then reads its file list from standard input.
Script:
#!/bin/bash
IFS=','
i=0
for j in `cat database | head -n 1`; do
variables[$i]=$j
i=`expr $i + 1`
done
k=0
for l in `cat database | tail -n $(expr $(cat database | wc -l) - 1)`; do
echo -n $k
k=`expr $k + 1`
if [ $k -eq 3 ]; then
k=0
fi
done
Input file
a,b,c
d,e,f
g,e,f
Output
01201
Expected output
012012
The question is why the for skips last echo? It is weird, because if I change $k to $l echo will run 6 times.
Update:
#thom's analysis is correct. You can fix the problem by changing IFS=',' to IFS=$',\n'.
My original statements below may be of general interest, but do not address the specific problem.
If accidental shell expansions were a concern, here's how the loop could be rewritten (assuming it's practical to read everything into an array variable first):
IFS=$',\n' read -d '' -r -a fields < <(echo $'*,b,c\nd,e,f\ng,h,i')
for field in "${fields[#]}"; do
# $field is '*' in 1st iteration, then 'b', 'c', 'd',...
done
Original statements:
Just a few general pointers:
You should use a while loop rather than for to read command output - see http://mywiki.wooledge.org/BashFAQ/001; the short of it: with for, the input lines are subject to various shell expansions.
A missing iteration typically stems from the last input line missing a terminating \n (or a separator as defined in $IFS). With a while loop, you can use the following approach to address this: while read -r line || [[ -n $line ]]; do …
For instance, your 2nd for loop could be rewritten as (using process substitution as input to avoid creating a subshell with a separate variable scope):
while read -r l || [[ -n $l ]]; do …; done < <(cat database | tail -n $(expr $(cat database | wc -l) - 1))
Finally, you could benefit from using modern bashisms: for instance,
k=`expr $k + 1`
could be rewritten much more succinctly as (( ++k )) (which will run faster, too).
Your code expects after EVERY read variable a comma but you only give this:
a,b,c
d,e,f
g,e,f
instead of this:
a,b,c,
d,e,f,
g,e,f,
so it reads:
d,e,f'\n'g,e,f
and that is equal to 5 values, not 6