test

Wat het doet

Zo schrijf je het

test EXPRESSION
[ EXPRESSION ]
[[ EXPRESSION ]]

Belangrijkste delen

Files

-e FILE

Exists (any type).

-f FILE

Is a regular file.

-d FILE

Is a folder.

-L FILE, -h FILE

Is a symbolic link.

-b FILE, -c FILE

Block / character device.

-p FILE, -S FILE

Named pipe / socket.

-s FILE

Exists and is not empty.

-r FILE, -w FILE, -x FILE

Readable / writable / executable for you.

-u FILE, -g FILE, -k FILE

SUID / SGID / sticky bit set.

-O FILE, -G FILE

Owned by you / by your group.

-N FILE

Changed since last read.

FILE1 -nt FILE2, FILE1 -ot FILE2

Newer / older than.

FILE1 -ef FILE2

Same file (hard link).

Strings

-z STRING

Empty.

-n STRING

Not empty.

S1 = S2, S1 != S2

Equal / not equal.

S1 S2, S1 S2

Sort order (escape in [ ]: \<).

S =~ REGEX

Matches a regular expression (only [[ ]]).

Numbers

N1 -eq N2, -ne

Equal / not equal.

N1 -lt N2, -le

Less / less or equal.

N1 -gt N2, -ge

Greater / greater or equal.

Logic

! EXPR

Not.

EXPR1 -a EXPR2, EXPR1 -o EXPR2

And / or (old; better: [ A ] && [ B ]).

&&, ||

And / or inside [[ ]].

-v NAME

The variable is set (bash).

$ als gewone gebruiker# als root (of met sudo)

1. 1Does a file exist?

   $[ -f /etc/fstab ] && echo "yes"
   yes

   Spaces inside the brackets are required.

2. 2In an if

   $if [ -d /backup ]; then echo "backup folder ok"; else mkdir /backup; fi

   -d = folder.

3. 3Compare strings

   $[ "$USER" = "root" ] || echo "run as root"

   Quote variables: empty values break [ = root ].

4. 4Compare numbers

   $[ $(df --output=pcent / | tail -1 | tr -dc 0-9) -gt 80 ] && echo "disk almost full"

   -gt for numbers, not >.

5. 5Check the number of arguments

   $set -- a b; [ $# -eq 2 ] && echo "two arguments"

   Common at the start of scripts.

6. 6Empty variable

   $NAME=""; [ -z "$NAME" ] && echo "empty"

   -n for not empty.

7. 7Pattern match with [[ ]]

   $FILE=report.csv; [[ $FILE == *.csv ]] && echo "CSV file"

   Wildcards work only in [[ ]].

8. 8Regular expression

   $IP=192.168.122.10; [[ $IP =~ ^([0-9]{1,3}\.){3}[0-9]{1,3}$ ]] && echo "looks like an IPv4"

   =~ in [[ ]].

9. 9Find world-writable scripts (security)

   $for f in /usr/local/bin/*; do [ -w "$f" ] && [ "$(stat -c %a "$f" | cut -c3)" -ge 2 ] && echo "$f is world-writable"; done

   Anybody could change these scripts.

10. 10Is a file newer than another?

    $[ /etc/nginx/nginx.conf -nt /var/run/nginx.pid ] && echo "config changed since start"

    Reload needed.

11. 11Exit status of test

    $test 5 -gt 3; echo $?
    0

    0 = true, 1 = false.

Niets past bij dit filter.

Exitcodes