###
Shell Script `-z`
Operator U
sage and Examples
In
shell scripting, the `-z` string
operator tests wheth
er a given string is empty (z
ero length). If the string has z
ero charact
ers, the condition evaluates as true; oth
erwise, false.
#### Example of Using `-z`
To demonstrate using `-z`, consid
er checking if an input argument was provided:
```
bash
#!/bin/
bash
input="$1"
if [ -z "$input" ]; then
echo "No arguments supplied."
else
echo "Argument received: $input"
fi
```
The above code snippet checks for the presence of command-line arguments passed to the script. When no argument exists (`$1`), `-z` returns true, leading to output indicating that no arguments w
ere supplied[^1].
Anoth
er practical application involves validating us
er inputs before processing them furth
er within scripts. This ensures required data points are present prior to execution logic proceeding.
For instance, ensuring both `proj` and `id` variables contain values could look like this:
```
bash
project="$1"
identifi
er="$2"
if [ -z "$project" ] || [ -z "$identifi
er" ]; then
echo -e "\nParamet
er error.\nThe u
sage: ./script.sh <proj> <id>"
exit 1
fi
```
H
ere, eith
er missing value trigg
ers an informative mes
sage regarding prop
er invocation syntax followed by t
ermination with status `1`.
--related questions--
1. How does one check multiple conditions involving strings in
bash?
2. What alt
ernatives exist besides `-z` for testing string prop
erties in
shell scripts?
3. Can you provide scenarios wh
ere combining `-z` with oth
er operators enhances validation routines?
扫一扫
4330
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
