I did
a=1234
let "a=a+1"
on command line and it's fine. But when I do the same in a shell script. It prints out an error that "let: not found". Here is the script file.
#!/bin/sh
a=1234;
let "a=a+1";
echo "$a";
Thanks,
8 Answers
Do not use let. Use POSIX arithmetic expansion: a=$(($a+1)). This is guaranteed to work in any POSIX-compliant shell.
1 Comment
daniel
This is the best solution
The problem is likely that /bin/sh is not the same as, or does not behave the same as, your normal shell. For example, when bash is invoked as /bin/sh, it provides a subset of its normal features.
So, you may need to change your shebang line to use a different shell:
#!/bin/bash
or
#!/bin/ksh
You don't need the semi-colons at the ends of the lines.
answered Jun 30, 2011 at 14:42
Jonathan Leffler
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Comments
See at: http://www.hlevkin.com/Shell_progr/hellobash.htm
The correct is:
a=1234;
b=1;
a=`expr $a + $b`;
1 Comment
Radagast the Brown
Thanks!!! this worked for me even on bare
sh in an alpine container, however - the provided link is brokenYou should use let a=a+1 without quotes
Comments
It's the '$a' of '$a=1234' that is killing you.
The shell does all $ substitutions and THEN evaluates the expression. As a result it saw "=1234" because there was no value to $a.
Use -x to see this.
bash -x your-script
Comments
Check your actual shell with the following command in the command line:
echo $SHELL
It will provide a shell name, use that instead of /bin/sh at the first line of your script.
1 Comment
John Eipe
yes the problem was with the shebang. I changed it to #!/bin/bash (echo $SHELL prints bash) and it works. But what is the purpose of shebang then? I thought it invokes the appropriate shell for executing the script. (I have sh in /bin). Or is it that let is not supported in bourne shell?
Check the shell name using
echo $SHELLChange the first line of the script accordingly to
#!/bin/bashor
#!/bin/kshinstead of
#!/bin/sh.
Comments
c=1
d=1
for i in `ls`
do
if [ -f $i ]
then
echo "$c -> $i"
c=`expr $c + 1`
fi
done
c=`expr $c - 1`
echo no. of files $c
for i in `ls`
do
if [ -d $i ]
then
echo "$d -> $i"
d=`expr $d + 1`
fi
done
d=`expr $d - 1`
echo no. of direcrories $d
1 Comment
Toby Speight
Welcome to Stack Overflow! Although this code may help to solve the problem, it doesn't explain why and/or how it answers the question. Providing this additional context would significantly improve its long-term educational value. Please edit your answer to add explanation, including what limitations and assumptions apply.
a=1234? Check this:help|grep lettoo.echo $SHELL- What it says?#~/bin/shis getting you the bourne shell. From your command line (when it works withlet), typeecho $SHELLand use that for your#!/bin/.... Good luck.