bash Bad Substitution

Question

bin bash  jobname  quot job 201312161447 0003 quot  jobname pre   jobname 0 16  jobname post   jobname 17   This bash script gives me  Bad substitution  error on Ubuntu  Any help will be highly appreciated

User · Answer

I have found that this issue is either caused by the marked answer or you have a line or space before the bash declaration

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Your script syntax is valid bash and good   Possible causes for the failure    Your bash is not really bash but ksh or some other shell which doesn t understand bash s parameter substitution  Because your script looks fine and works with bash  Do ls -l  bin bash and check it s really bash and not sym-linked to some other shell  If you do have bash on your system  then you may be executing your script the wrong way like  ksh script sh or sh script sh  and your default shell is not bash   Since you have proper shebang  if you have bash   script sh or bash   script sh should be fine

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I was adding a dollar sign twice in an expression with curly braces in bash   cp -r  PROJECT NAME    PROJECT NAME 2   instead of  cp -r  PROJECT NAME   PROJECT NAME 2

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Not relevant to your example  but you can also get the Bad substitution error in Bash for any substitution syntax that Bash does not recognize  This could be    Stray whitespace  E g  bash -c    x    A typo  E g  bash -c    x -   A feature that was added in a later Bash version  E g  bash -c    x Q   before Bash 4 4    If you have multiple substitutions in the same expression  Bash may not be very helpful in pinpointing the problematic expression  E g      bash -c     x   multiline string  y   bash  line 1    x   multiline string  y  bad substitution

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For others that arrive here  this exact message will also appear when using the env variable syntax for commands  for example   which sh  instead of the correct   which sh

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Looks like   x  causes problems   root raspi1    cat  gt   tmp btest    bin bash  jobname  job 201312161447 0003  jobname pre   jobname 0 16  jobname post   jobname 17  root raspi1    chmod  x  tmp btest root raspi1     tmp btest root raspi1    sh -x  tmp btest   jobname job 201312161447 0003  tmp btest  4   tmp btest  Bad substitution

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I agree with Ahmed and RavinderSingh13 I had a similar problem and found that a white space was just before  quot    bin bash quot  at the first line of some of my scripts  I never understood how this space appeared but all my script has at least one space at beginning of any line

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Also  make sure you don t have an empty string for the first line of your script    i e  make sure    bin bash is the very first line of your script

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Both - bash or dash - work  but the syntax needs to be   FILENAME  my complex path name ext NEWNAME   FILENAME ext new

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in my case  under ubuntu 18 04   I have mixed          that works fine  BACKUPED NB   ls   HOST BACKUP DIR    CONTAINER NAME  backup sql gz   wc --lines   full example here

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I had the same problem  Make sure your script didnt have      bin sh    at the top of your script  Instead  you should add      bin bash

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Try running the script explicitly using bash command rather than just executing it as executable

User · Answer

The default shell   bin sh  under Ubuntu points to dash  not bash   me pc    readlink -f   which sh   bin dash   So if you chmod  x your script file sh and then run it with   your script file sh  or if you run it with bash your script file sh  it should work fine   Running it with sh your script file sh will not work because the hashbang line will be ignored and the script will be interpreted by dash  which does not support that string substitution syntax

[string] bash: Bad Substitution

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