Shell Script – How to Delete the Last Character of a String

shell-scriptstring

I would like to delete the last character of a string, I tried this little script :

#! /bin/sh 

t="lkj"
t=${t:-2}
echo $t

but it prints "lkj", what I am doing wrong?

Best Answer

In a POSIX shell, the syntax ${t:-2} means something different - it expands to the value of t if t is set and non null, and otherwise to the value 2. To trim a single character by parameter expansion, the syntax you probably want is ${t%?}

Note that in ksh93, bash or zsh, ${t:(-2)} or ${t: -2} (note the space) are legal as a substring expansion but are probably not what you want, since they return the substring starting at a position 2 characters in from the end (i.e. it removes the first character i of the string ijk).

See the Shell Parameter Expansion section of the Bash Reference Manual for more info:

Bash Reference Manual – Shell Parameter Expansion

Related Solutions

Bash – Extracting a string, according to a pattern, in a bash script

You can use a regex in bash (3.0 or above) to accomplish this:

if [[ $strname =~ 3(.+)r ]]; then
    strresult=${BASH_REMATCH[1]}
else
    echo "unable to parse string $strname"
fi

In bash, capture groups from a regex are placed in the special array BASH_REMATCH. Element 0 contains the entire match, and 1 contains the the match for the first capture group.

C Shell – Condition for If String Contains a Newline Character

if ($mystr:q =~ *'\
'*) echo yes

should work in some implementations and versions of csh (like the csh and tcsh ones found on Debian). In some others (like the one found on Solaris 10), you may have better luck with

set nl = '\
'
if ($mystr:q =~ *$nl:q*) echo yes

Most people have given up trying to write reliable scripts with csh by now. Why would you use csh in this century?

This code works for me (outputs no) in tcsh 6.17.00 (Astron) 2009-07-10 (x86_64-unknown-linux) options wide,nls,dl,al,kan,rh,color,filec

set mystr = '1234ABC\
 -------\
FOOBAR'
if ($mystr:q !~ *'\
'*) then
  echo yes
else
  echo no
endif

Note that if you do:

set var = `some command`

csh stores each word (blank separated) of the output of some command in several elements of the var array.

With:

set var = "`some command`"

it stores each non-empty line in elements of the array.

It looks like one cannot¹ store the output of a command whole into a variable in (t)csh, so your only option would be:

set var = "`some command`" # note that it removes the empty lines
if ($#var == 1)...

¹ Strictly speaking, that's not true, one could do something like:

set x = "`some command | paste -d. /dev/null -`"
set var = ""
set nl = '\
'

foreach i ($x:q)
  set i = $i:s/.//:q
  set var = $var:q$i:q$nl:q
end

^{(of course, it may not work in all csh implementations/versions)}

Best Answer

Related Solutions

Bash – Extracting a string, according to a pattern, in a bash script

C Shell – Condition for If String Contains a Newline Character

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