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How to check if a string contains a substring in Bash
(29 answers)
Closed 3 years ago.
I am wanting to use a switch/ case statement in bash to check if a file name which is a string contains something but also does not.
Here is my case:
case "$fileName" in
*Failed|!cp*)
echo "match"
;;
esac
But this does not work currently, how can I see if the string matches "Failed" but also does not contain "cp"?
It would be great if this could be done in a switch/ case as well
! has to be followed by a parenthesized list of patterns, not the pattern itself.
| in a case is for OR, not AND. To get AND, you should nest cases.
case "$fileName" in
*Failed)
case "$fileName" in
cp*) ;;
*) echo "match" ;;
esac
;;
esac
Or you could just use if instead of case:
if [[ $filename = *Failed && $filename != cp* ]]
then echo match
fi
Alternatively you can use if and pipes for instance:
if echo 'Failed' | grep -v cp | grep -q Failed ; then
echo Failed without cp
else
echo It's either Winned or cp.
fi
I need to make a script that iterates through a list of parameters and checks/counts if the parameter starts with an uppercase letter. I have some starter code but I am stuck and would appreciate any help!
Several notes:
You're missing the =~ operator for a regular expression
Your if is not ended by a fi.
Using [A-Z] doesn't work in all locales, and is needlessly fragile. Some collation orders are of the form AaBbCcDd, and thus A-Z contains a, b, etc; [[:upper:]] is guaranteed to do the right thing everywhere.
Unquoted $# behaves exactly the same as unquoted $*. If you want to correctly honor the quoting and escaping used when your function was first called, use "$#", quoted.
Consider instead:
#!/bin/bash
(( "$#" )) || { echo "Error: No arguments given" >&2; exit 1; }
re='^[[:upper:]]' # store regex in a variable for compatibility with old bash releases
for word in "$#"; do
[[ $word =~ $re ]] && ((++count))
done
echo "$count arguments started with upper-case characters"
Alternately, by using a case statement you can avoid requiring bash, and also check for other types:
for word in "$#"; do
case $word in
[[:upper:]]*) (( ++upper_count )) ;;
[[:lower:]]*) (( ++lower_count )) ;;
[[:digit:]]*) (( ++digit_count )) ;;
esac
done
echo "Found $upper_count arguments starting with upper-case letters"
echo "Found $lower_count arguments starting with lower-case letters"
echo "Found $digit_count arguments starting with digits"
#! /bin/bash
if [ $# -eq 0 ]; then
echo Error
exit 1
fi
COUNT=`echo "$#" | tr ' ' '\n' | grep "^[A-Z]" | wc -l`
echo $COUNT
I have the following strings in bash
str1="any string"
str2="any"
I want to check if str2 is a substring of str1
I can do it in this way:
c=`echo $str1 | grep $str2`
if [ $c != "" ]; then
...
fi
Is there a more efficient way of doing this?
You can use wild-card expansion *.
str1="any string"
str2="any"
if [[ "$str1" == *"$str2"* ]]
then
echo "str2 found in str1"
fi
Note that * expansion will not work with single [ ].
str1="any string"
str2="any"
Old school (Bourne shell style):
case "$str1" in *$str2*)
echo found it
esac
New school (as speakr shows), however be warned that the string to the right will be viewed as a regular expression:
if [[ $str1 =~ $str2 ]] ; then
echo found it
fi
But this will work too, even if you're not exactly expecting it:
str2='.*[trs].*'
if [[ $str1 =~ $str2 ]] ; then
echo found it
fi
Using grep is slow, since it spawns a separate process.
You can use bash regexp matching without using grep:
if [[ $str1 =~ $str2 ]]; then
...
fi
Note that you don't need any surrounding slashes or quotes for the regexp pattern. If you want to use glob pattern matching just use == instead of =~ as operator.
Some examples can be found here.
if echo $str1 | grep -q $str2 #any command
then
.....
fi
I am trying to write a script in bash that check the validity of a user input.
I want to match the input (say variable x) to a list of valid values.
what I have come up with at the moment is:
for item in $list
do
if [ "$x" == "$item" ]; then
echo "In the list"
exit
fi
done
My question is if there is a simpler way to do this,
something like a list.contains(x) for most programming languages.
Say list is:
list="11 22 33"
my code will echo the message only for those values since list is treated as an array and not a string,
all the string manipulations will validate 1 while I would want it to fail.
[[ $list =~ (^|[[:space:]])$x($|[[:space:]]) ]] && echo 'yes' || echo 'no'
or create a function:
contains() {
[[ $1 =~ (^|[[:space:]])$2($|[[:space:]]) ]] && exit(0) || exit(1)
}
to use it:
contains aList anItem
echo $? # 0： match, 1: failed
how about
echo $list | grep -w -q $x
you could either check the output or $? of above line to make the decision.
grep -w checks on whole word patterns. Adding -q prevents echoing the list.
Matvey is right, but you should quote $x and consider any kind of "spaces" (e.g. new line) with
[[ $list =~ (^|[[:space:]])"$x"($|[[:space:]]) ]] && echo 'yes' || echo 'no'
so, i.e.
# list_include_item "10 11 12" "2"
function list_include_item {
local list="$1"
local item="$2"
if [[ $list =~ (^|[[:space:]])"$item"($|[[:space:]]) ]] ; then
# yes, list include item
result=0
else
result=1
fi
return $result
}
end then
`list_include_item "10 11 12" "12"` && echo "yes" || echo "no"
or
if `list_include_item "10 11 12" "1"` ; then
echo "yes"
else
echo "no"
fi
Note that you must use "" in case of variables:
`list_include_item "$my_list" "$my_item"` && echo "yes" || echo "no"
IMHO easiest solution is to prepend and append the original string with a space and check against a regex with [[ ]]
haystack='foo bar'
needle='bar'
if [[ " $haystack " =~ .*\ $needle\ .* ]]; then
...
fi
this will not be false positive on values with values containing the needle as a substring, e.g. with a haystack foo barbaz.
(The concept is shamelessly stolen form JQuery's hasClass()-Method)
You can use (* wildcards) outside a case statement, too, if you use double brackets:
string='My string';
if [[ $string == *My* ]]
then
echo "It's there!";
fi
If it isn't too long; you can just string them between equality along a logical OR comparison like so.
if [ $ITEM == "item1" -o $ITEM == "item2" -o $ITEM == "item3" ]; then
echo In the list
fi
I had this exact problem and while the above is ugly it is more obvious what is going on than the other generalized solutions.
If your list of values is to be hard-coded in the script, it's fairly simple to test using case. Here's a short example, which you can adapt to your requirements:
for item in $list
do
case "$x" in
item1|item2)
echo "In the list"
;;
not_an_item)
echo "Error" >&2
exit 1
;;
esac
done
If the list is an array variable at runtime, one of the other answers is probably a better fit.
There's a cleaner way to check if string is in the list:
if [[ $my_str = #(str1|str2|str3) ]]; then
echo "string found"
fi
Consider exploiting the keys of associative arrays. I would presume this outperforms both regex/pattern matching and looping, although I haven't profiled it.
declare -A list=( [one]=1 [two]=two [three]='any non-empty value' )
for value in one two three four
do
echo -n "$value is "
# a missing key expands to the null string,
# and we've set each interesting key to a non-empty value
[[ -z "${list[$value]}" ]] && echo -n '*not* '
echo "a member of ( ${!list[*]} )"
done
Output:
one is a member of ( one two three )
two is a member of ( one two three )
three is a member of ( one two three )
four is *not* a member of ( one two three )
If the list is fixed in the script, I like the following the best:
validate() {
grep -F -q -x "$1" <<EOF
item 1
item 2
item 3
EOF
}
Then use validate "$x" to test if $x is allowed.
If you want a one-liner, and don't care about whitespace in item names, you can use this (notice -w instead of -x):
validate() { echo "11 22 33" | grep -F -q -w "$1"; }
Notes:
This is POSIX sh compliant.
validate does not accept substrings (remove the -x option to grep if you want that).
validate interprets its argument as a fixed string, not a regular
expression (remove the -F option to grep if you want that).
Sample code to exercise the function:
for x in "item 1" "item2" "item 3" "3" "*"; do
echo -n "'$x' is "
validate "$x" && echo "valid" || echo "invalid"
done
I find it's easier to use the form echo $LIST | xargs -n1 echo | grep $VALUE as illustrated below:
LIST="ITEM1 ITEM2"
VALUE="ITEM1"
if [ -n "`echo $LIST | xargs -n1 echo | grep -e \"^$VALUE`$\" ]; then
...
fi
This works for a space-separated list, but you could adapt it to any other delimiter (like :) by doing the following:
LIST="ITEM1:ITEM2"
VALUE="ITEM1"
if [ -n "`echo $LIST | sed 's|:|\\n|g' | grep -e \"^$VALUE`$\"`" ]; then
...
fi
Note that the " are required for the test to work.
Thought I'd add my solution to the list.
# Checks if element "$1" is in array "$2"
# #NOTE:
# Be sure that array is passed in the form:
# "${ARR[#]}"
elementIn () {
# shopt -s nocasematch # Can be useful to disable case-matching
local e
for e in "${#:2}"; do [[ "$e" == "$1" ]] && return 0; done
return 1
}
# Usage:
list=(11 22 33)
item=22
if elementIn "$item" "${list[#]}"; then
echo TRUE;
else
echo FALSE
fi
# TRUE
item=44
elementIn $item "${list[#]}" && echo TRUE || echo FALSE
# FALSE
The shell built-in compgen can help here. It can take a list with the -W flag and return any of the potential matches it finds.
# My list can contain spaces so I want to set the internal
# file separator to newline to preserve the original strings.
IFS=$'\n'
# Create a list of acceptable strings.
accept=( 'foo' 'bar' 'foo bar' )
# The string we will check
word='foo'
# compgen will return a list of possible matches of the
# variable 'word' with the best match being first.
compgen -W "${accept[*]}" "$word"
# Returns:
# foo
# foo bar
We can write a function to test if a string equals the best match of acceptable strings. This allows you to return a 0 or 1 for a pass or fail respectively.
function validate {
local IFS=$'\n'
local accept=( 'foo' 'bar' 'foo bar' )
if [ "$1" == "$(compgen -W "${accept[*]}" "$1" | head -1)" ] ; then
return 0
else
return 1
fi
}
Now you can write very clean tests to validate if a string is acceptable.
validate "blah" || echo unacceptable
if validate "foo" ; then
echo acceptable
else
echo unacceptable
fi
Prior answers don't use tr which I found to be useful with grep. Assuming that the items in the list are space delimited, to check for an exact match:
echo $mylist | tr ' ' '\n' | grep -F -x -q "$myitem"
This will return exit code 0 if the item is in the list, or exit code 1 if it isn't.
It's best to use it as a function:
_contains () { # Check if space-separated list $1 contains line $2
echo "$1" | tr ' ' '\n' | grep -F -x -q "$2"
}
mylist="aa bb cc"
# Positive check
if _contains "${mylist}" "${myitem}"; then
echo "in list"
fi
# Negative check
if ! _contains "${mylist}" "${myitem}"; then
echo "not in list"
fi
Late to the show? Following very easy variant was not clearly mentioned yet. I use case for checking simple lists, which is a general Bourne Shell idiom not relying on anything external nor extended:
haystack='a b c'
needle='b'
case " $haystack " in (*" $needle "*) :;; (*) false;; esac
Please note the use of the separator (here: SPC) to correcyly delimit the pattern: At the beginning and end of " $haystack " and likewise in the test of " $needle ".
This statement returns true ($?=0) in case $needle is in $haystack, false otherwise.
Also you can test for more than one $needle very easily. When there are several similar cases like
if (haystack.contains(needle1)) { run1() } elif (haystack.contains(needle2)) { run2() } else { run3() }
you can wrap this into the case, too:
case " $haystack " in (*" $needle1 "*) run1;; (*" $needle2 "*) run2;; (*) run3;; esac
and so on
This also works for all lists with values which do not include the separator itself, like comma:
haystack=' a , b , c '
needle=' b '
case ",$haystack," in (*",$needle,"*) :;; (*) false;; esac
Note that if values can contain anything including the separator sequence (except NUL, as shells do not suport NUL in variables as you cannot pass arguments containing NUL to commands) then you need to use arrays. Arrays are ksh/bashisms and not supported by "ordinary" POSIX/Bourne shells. (You can work around this limitation using $# in POSIX-Shells, but this is something completely different than what was aked here.)
Can the (*) false part be left away?
No, as this is the critical return value. By default case returns true.
Yes if you do not need the return value and put your processing at the location of the :
Why the :;;
We could also write true;;, but I am used to use : instead of true because it is shorter and faster to type
Also I consider not writing anything bad practice, as it is not obvious to everybody that the default return value of case is true.
Also "leaving out" the command usually indicates "something was forgotten here". So putting a redundant ":" there clearly indicates "it is intended to do nothing else than return true here".
In bash you can also use ksh/bashisms like ;& (fallthroug) or ;;& (test other patterns) to express if (haystack.contains(needle1)) { run1(); }; if (haystack.contains(needle2)) { run2(); }
Hence usually case is much more maintainable than other regex constructs. Also it does not use regex, it only use shell patterns, which might even be faster.
Reusable function:
: Needle "list" Seperator_opt
NeedleListSep()
{
if [ 3 -gt $# ];
then NeedleListSep "$1" "$2" " ";
else case "$3$2$3" in (*"$3$1$3"*) return 0;; esac; return 1;
fi;
}
In bash you can simplify this to
: Needle "list" Seperator_opt
NeedleListSep()
{
local s="${3-" "}";
case "$s$2$s" in (*"$s$1$s"*) return 0;; esac; return 1;
}
Use like this
Test() {
NeedleListSep "$1" "a b c" && echo found $1 || echo no $1;
NeedleListSep "$1" "a,b,c" ',' && echo found $1 || echo no $1;
NeedleListSep "$1" "a # b # c" ' # ' && echo found $1 || echo no $1;
NeedleListSep "$1" "abc" '' && echo found $1 || echo no $1;
}
Test a
Test z
As shown above, this also works for degerated cases where the separator is the empty string (so each character of the list is a needle). Example:
Test
returns
no
no
no
found
As the empty string is cleary part of abc in case your separator is the empty string, right?
Note that this function is Public Domain as there is absolutely nothing to it which can be genuinely copyrighted.
An alternative solution inspired by the accepted response, but that uses an inverted logic:
MODE="${1}"
echo "<${MODE}>"
[[ "${MODE}" =~ ^(preview|live|both)$ ]] && echo "OK" || echo "Uh?"
Here, the input ($MODE) must be one of the options in the regular expression ('preview', 'live', or 'both'), contrary to matching the whole options list to the user input. Of course, you do not expect the regular expression to change.
Examples
$ in_list super test me out
NO
$ in_list "super dude" test me out
NO
$ in_list "super dude" test me "super dude"
YES
# How to use in another script
if [ $(in_list $1 OPTION1 OPTION2) == "NO" ]
then
echo "UNKNOWN type for param 1: Should be OPTION1 or OPTION2"
exit;
fi
in_list
function show_help()
{
IT=$(CAT <<EOF
usage: SEARCH_FOR {ITEM1} {ITEM2} {ITEM3} ...
e.g.
a b c d -> NO
a b a d -> YES
"test me" how "test me" -> YES
)
echo "$IT"
exit
}
if [ "$1" == "help" ]
then
show_help
fi
if [ "$#" -eq 0 ]; then
show_help
fi
SEARCH_FOR=$1
shift;
for ITEM in "$#"
do
if [ "$SEARCH_FOR" == "$ITEM" ]
then
echo "YES"
exit;
fi
done
echo "NO"
Assuming TARGET variable can be only 'binomial' or 'regression', then following would do:
# Check for modeling types known to this script
if [ $( echo "${TARGET}" | egrep -c "^(binomial|regression)$" ) -eq 0 ]; then
echo "This scoring program can only handle 'binomial' and 'regression' methods now." >&2
usage
fi
You could add more strings into the list by separating them with a | (pipe) character.
Advantage of using egrep, is that you could easily add case insensitivity (-i), or check more complex scenarios with a regular expression.
This is almost your original proposal but almost a 1-liner. Not that complicated as other valid answers, and not so depending on bash versions (can work with old bashes).
OK=0 ; MP_FLAVOURS="vanilla lemon hazelnut straciatella"
for FLAV in $MP_FLAVOURS ; do [ $FLAV == $FLAVOR ] && { OK=1 ; break; } ; done
[ $OK -eq 0 ] && { echo "$FLAVOR not a valid value ($MP_FLAVOURS)" ; exit 1 ; }
I guess my proposal can still be improved, both in length and style.
Simple oneliner...
if [[ " 11 22 33 " == *" ${x} "* ]]; then echo "${x} is in the list"; fi;
Add before fi: else echo "${x} is NOT in the list";
The script below implements contains function for a list.
function contains {
local target=$1
shift
printf '%s\n' "$#" | grep -x -q "$target"
out=$?
(( out = 1 - out ))
return $out
}
If you convert a string based on white space into a list and use it, it seems to be solved as follows.
list="11 22 33"
IFS=" " read -ra parsed_list <<< "$list"
# parsed_list would be ("11" "22" "33")
contains "11" "${parsed_list[#]}"
echo $? # 1
contains "22" "${parsed_list[#]}"
echo $? # 1
contains "1" "${parsed_list[#]}"
echo $? # 0
contains "11 22" "${parsed_list[#]}"
echo $? # 0
The == operator is used to compare two strings in shell script. However, I want to compare two strings ignoring case, how can it be done? Is there any standard command for this?
In Bash, you can use parameter expansion to modify a string to all lower-/upper-case:
var1=TesT
var2=tEst
echo ${var1,,} ${var2,,}
echo ${var1^^} ${var2^^}
All of these answers ignore the easiest and quickest way to do this (as long as you have Bash 4):
if [ "${var1,,}" = "${var2,,}" ]; then
echo ":)"
fi
All you're doing there is converting both strings to lowercase and comparing the results.
if you have bash
str1="MATCH"
str2="match"
shopt -s nocasematch
case "$str1" in
$str2 ) echo "match";;
*) echo "no match";;
esac
otherwise, you should tell us what shell you are using.
alternative, using awk
str1="MATCH"
str2="match"
awk -vs1="$str1" -vs2="$str2" 'BEGIN {
if ( tolower(s1) == tolower(s2) ){
print "match"
}
}'
Save the state of nocasematch (in case some other function is depending on it being disabled):
local orig_nocasematch=$(shopt -p nocasematch; true)
shopt -s nocasematch
[[ "foo" == "Foo" ]] && echo "match" || echo "notmatch"
$orig_nocasematch
Note that local is only required inside a function.
Also, the ; true part will prevent the shell from exiting when set -e is on and $(shopt -p nocasematch) fails (because nocasematch was NOT set at all).
One way would be to convert both strings to upper or lower:
test $(echo "string" | /bin/tr '[:upper:]' '[:lower:]') = $(echo "String" | /bin/tr '[:upper:]' '[:lower:]') && echo same || echo different
Another way would be to use grep:
echo "string" | grep -qi '^String$' && echo same || echo different
For zsh the syntax is slightly different, but still shorter than most answers here:
> str1='mAtCh'
> str2='MaTcH'
> [[ "$str1:u" = "$str2:u" ]] && echo 'Strings Match!'
Strings Match!
>
This will convert both strings to uppercase before the comparison.
Another method makes use zsh's globbing flags, which allows us to directly make use of case-insensitive matching by using the i glob flag:
setopt extendedglob
[[ $str1 = (#i)$str2 ]] && echo "Match success"
# this example compares the variable with a literal string 'match'
[[ $str1 = (#i)match ]] && echo "Match success"
I came across this great blog/tutorial/whatever about dealing with case sensitive pattern. The following three methods are explained in details with examples:
1. Convert pattern to lowercase using tr command
opt=$( tr '[:upper:]' '[:lower:]' <<<"$1" )
case $opt in
sql)
echo "Running mysql backup using mysqldump tool..."
;;
sync)
echo "Running backup using rsync tool..."
;;
tar)
echo "Running tape backup using tar tool..."
;;
*)
echo "Other options"
;;
esac
2. Use careful globbing with case patterns
opt=$1
case $opt in
[Ss][Qq][Ll])
echo "Running mysql backup using mysqldump tool..."
;;
[Ss][Yy][Nn][Cc])
echo "Running backup using rsync tool..."
;;
[Tt][Aa][Rr])
echo "Running tape backup using tar tool..."
;;
*)
echo "Other option"
;;
esac
3. Turn on nocasematch
opt=$1
shopt -s nocasematch
case $opt in
sql)
echo "Running mysql backup using mysqldump tool..."
;;
sync)
echo "Running backup using rsync tool..."
;;
tar)
echo "Running tape backup using tar tool..."
;;
*)
echo "Other option"
;;
esac
shopt -u nocasematch
For korn shell, I use typeset built-in command (-l for lower-case and -u for upper-case).
var=True
typeset -l var
if [[ $var == "true" ]]; then
print "match"
fi
Very easy if you fgrep to do a case-insensitive line compare:
str1="MATCH"
str2="match"
if [[ $(fgrep -ix $str1 <<< $str2) ]]; then
echo "case-insensitive match";
fi
Here is my solution using tr:
var1=match
var2=MATCH
var1=`echo $var1 | tr '[A-Z]' '[a-z]'`
var2=`echo $var2 | tr '[A-Z]' '[a-z]'`
if [ "$var1" = "$var2" ] ; then
echo "MATCH"
fi
grep has a -i flag which means case insensitive so ask it to tell you if var2 is in var1.
var1=match
var2=MATCH
if echo $var1 | grep -i "^${var2}$" > /dev/null ; then
echo "MATCH"
fi
shopt -s nocaseglob
The 'tr' utility (translate characters) is always present on all Unix/Linux machines, and is light-weight.
Here is a function that can be used to address case insensitive comparisons. Since the exact location of 'tr' can vary, we first probe its likely locations and store the correct location in an env var appropriately named "BIN_TR".
declare BIN_TR=$( ls /bin/tr /usr/bin/tr 2>/dev/null | head -1 );
That is then used in the function declaration.
toLowerCase() {
echo "$*" | $BIN_TR '[:upper:]' '[:lower:]'
}
A solution using 'tr' is expected to be highly portable between different variations of OS and OS set-up. While 'awk' is also highly probable, the 'tr' utility is tiny compared to 'awk', and so a function using 'tr' is presumably lighter weight.
On Unix-like operating systems, the test command checks file types and compares values.
str1="MATCH"
str2="match"
if test $str1 = $str2
then
echo "equal yes"
else
echo "equal not"
fi
On Unix-like operating systems, the test command checks file types and compares values.
it's very simple that way.
in a few lines of code