I wonder if there is any way to execute script with argument that can be optional.
For example
./script (optional parameter X) path
So typing ./script /Users/name/Documents would execute certain function (I assume that if statement will be crucial) and ./script X Users/mcichecki/Documents will execute another function.
I was trying to do it with optional arguments and it didn't work:
ARG1=${1:-R}
if [ "$1" = "X" ];
then
first_function
else
second_function
fi
If the optional argument were last you could use default values. It doesn't work so well when it is first.
Use $# to check the number of arguments that were passed in.
case $# in
1) ARG1=-R; ARG2=$1;;
2) ARG1=$1; ARG2=$2;;
*) echo "Usage: $0 [parameterX] path" >&2; exit 1;;
esac
Related
How do you pass arguments to custom zsh functions?
For instance:
function kill_port_proc(port) {
lsof -i tcp:<port interpolated here>| grep LISTEN | awk '{print $2}'
}
I'm seeing so many examples online with ZSH functions, but there barely anything on passing arguments and interpolating them.
When defining a function, you cannot specify required arguments. That's why using both the function keyword and parens () seems useless to me.
To get the passed arguments, use positional parameters.
The positional parameters provide access to the command-line arguments of a shell function, shell script, or the shell itself; [...]
The parameter n, where n is a number, is the nth positional parameter. The parameter $0 is a special case [...]
About the $0 positional parameter:
The name used to invoke the current shell, or as set by the -c command line option upon invocation.
If the FUNCTION_ARGZERO option is set, $0 is set upon entry to a shell function to the name of the function, and upon entry to a sourced script to the name of the script, and reset to its previous value when the function or script returns.
Using your example:
function kill_port_proc {
lsof -i tcp:"$1" | grep LISTEN | awk '{print $2}'
}
Personaly, I like to document the function by, at least, adding the function signature prior to the definition.
Then, I declare local parameters for each arguments and readonly parameters when I want to protect them from unexpected modification.
If the argument is mandatory, I use a special parameter expansion form:
${name?word}
${name:?word}
In the first form, if name is set, or in the second form if name is both set and non-null, then substitute its value;
otherwise, print word and exit from the shell. Interactive shells instead return to the prompt.
If word is omitted, then a standard message is printed.
How I would write your example:
# kill_port_proc <port>
function kill_port_proc {
readonly port=${1:?"The port must be specified."}
lsof -i tcp:"$port" | grep LISTEN | awk '{print $2}'
}
my_function() {
if [ $# -lt 2 ]
then
echo "Usage: $funcstack[1] <first-argument> <second-argument>"
return
fi
echo "First argument: $1"
echo "Second argument: $2"
}
Usage
$ my_function
Usage: my_function <first-argument> <second-argument>
$ my_function foo
Usage: my_function <first-argument> <second-argument>
$ my_function foo bar
First argument: foo
Second argument: bar
I am able to use grep in normal command line.
grep "ABC" Filename -C4
This is giving me the desired output which is 4 lines above and below the matched pattern line.
But if I use the same command in a Unix shell script, I am unable to grep the lines above and below the pattern. It is giving me output as the only lines where pattern is matched and an error in the end that cannot says cannot open grep : -C4
The results are similar if I use -A4 and -B4
I'll assume you need a portable POSIX solution without the GNU extensions (-C NUM, -A NUM, and -B NUM are all GNU, as are arguments following the pattern and/or file name).
POSIX grep can't do this, but POSIX awk can. This can be invoked as e.g. grepC -C4 "ABC" Filename (assuming it is named "grepC", is executable, and is in your $PATH):
#!/bin/sh
die() { echo "$*\nUsage: $0 [-C NUMBER] PATTERN [FILE]..." >&2; exit 2; }
CONTEXT=0 # default value
case $1 in
-C ) CONTEXT="$2"; shift 2 ;; # extract "4" from "-C 4"
-C* ) CONTEXT="${1#-C}"; shift ;; # extract "4" from "-C4"
--|-) shift ;; # no args or use std input (implicit)
-* ) [ -f "$1" ] || die "Illegal option '$1'" ;; # non-option non-file
esac
[ "$CONTEXT" -ge 0 ] 2>/dev/null || die "Invalid context '$CONTEXT'"
[ "$#" = 0 ] && die "Missing PATTERN"
PATTERN="$1"
shift
awk '
/'"$PATTERN"'/ {
match='$CONTEXT'
for(i=1; i<=CONTEXT; i++) if(NR>i) print last[i];
print
next
}
match { print; match-- }
{ for(i='$CONTEXT'; i>1; i--) last[i] = last[i-1]; last[1] = $0 }
' "$#"
This sets up die as a fatal error function, then finds the desired lines of context from your arguments (either -C NUMBER or -CNUMBER), with an error for unsupported options (unless they're files).
If the context is not a number or there is no pattern, we again fatally error out.
Otherwise, we save the pattern, shift it away, and reserve the rest of the options for handing to awk as files ("$#").
There are three stanzas in this awk call:
Match the pattern itself. This requires ending the single-quote portion of the string in order to incorporate the $PATTERN variable (which may not behave correctly if imported via awk -v). Upon that match, we store the number of lines of context into the match variable, loop through the previous lines saved in the last hash (if we've gone far enough to have had them), and print them. We then skip to the next line without evaluating the other two stanzas.
If there was a match, we need the next few lines for context. As this stanza prints them, it decrements the counter. A new match (previous stanza) will reset that count.
We need to save previous lines for recalling upon a match. This loops through the number of lines of context we care about and stores them in the last hash. The current line ($0) is stored in last[1].
I need to loop over environment variables and get their names and values in POSIX sh (not bash). This is what I have so far.
#!/usr/bin/env sh
# Loop over each line from the env command
while read -r line; do
# Get the string before = (the var name)
name="${line%=*}"
eval value="\$$name"
echo "name: ${name}, value: ${value}"
done <<EOF
$(env)
EOF
It works most of the time, except when an environment variable contains a newline. I need it to work in that case.
I am aware of the -0 flag for env that separates variables with nul instead of newlines, but if I use that flag, how do I loop over each variable? Edit: #chepner pointed out that POSIX env doesn't support -0, so that's out.
Any solution that uses portable linux utilities is good as long as it works in POSIX sh.
There is no way to parse the output of env with complete confidence; consider this output:
bar=3
baz=9
I can produce that with two different environments:
$ env -i "bar=3" "baz=9"
bar=3
baz=9
$ env -i "bar=3
> baz=9"
bar=3
baz=9
Is that two environment variables, bar and baz, with simple numeric values, or is it one variable bar with the value $'3\nbaz=9' (to use bash's ANSI quoting style)?
You can safely access the environment with POSIX awk, however, using the ENVIRON array. For example:
awk 'END { for (name in ENVIRON) {
print "Name is "name;
print "Value is "ENVIRON[name];
}
}' < /dev/null
With this command, you can distinguish between the two environments mentioned above.
$ env -i "bar=3" "baz=9" awk 'END { for (name in ENVIRON) { print "Name is "name; print "Value is "ENVIRON[name]; }}' < /dev/null
Name is baz
Value is 9
Name is bar
Value is 3
$ env -i "bar=3
> baz=9" awk 'END { for (name in ENVIRON) { print "Name is "name; print "Value is "ENVIRON[name]; }}' < /dev/null
Name is bar
Value is 3
baz=9
Maybe this would work?
#!/usr/bin/env sh
env | while IFS= read -r line
do
name="${line%%=*}"
indirect_presence="$(eval echo "\${$name+x}")"
[ -z "$name" ] || [ -z "$indirect_presence" ] || echo "name:$name, value:$(eval echo "\$$name")"
done
It is not bullet-proof, as if the value of a variable with a newline happens to have a line beginning that looks like an assignment, it could be somewhat confused.
The expansion uses %% to remove the longest match, so if a line contains several = signs, they should all be removed to leave only the variable name from the beginning of the line.
Here an example based on the awk approach:
#!/bin/sh
for NAME in $(awk "END { for (name in ENVIRON) { print name; }}" < /dev/null)
do
VAL="$(awk "END { printf ENVIRON[\"$NAME\"]; }" < /dev/null)"
echo "$NAME=$VAL"
done
#!/bin/bash
LOCATION=$1
FILECOUNT=0
DIRCOUNT=0
if [ "$#" -lt "1" ]
then
echo "Usage: ./test2.sh <directory>"
exit 0
fi
I don't actually get what the If statement is saying can anyone help me to explain this?Thank you
$1 refers to the first argument of the bash file. In this case, you can pass your directory path by issuing the following command:
# ./test2.sh /path/of/your/directory
#!/bin/bash
LOCATION=$1 #first argument of the script
FILECOUNT=0
DIRCOUNT=0
if [ "$#" -lt "1" ] #if the number of argument(s) ($#) is less than 1
then
echo "Usage: ./test2.sh <directory>"
exit 0
fi
You can read this article for more information about parameter passing.
Hope it helps.
$1 is the first argument that is passed to the bash script. If you start the script like ./test2.sh argument1 argument2 the $1 will refer argument1.
The if-statement checks, if the count of arguments (that's the $#) is smaller than 1, then it will output the usage statement (as it seems you can't run the script without any argument).
The following shell script takes a list of arguments, turns Unix paths into WINE/Windows paths and invokes the given executable under WINE.
#! /bin/sh
if [ "${1+set}" != "set" ]
then
echo "Usage; winewrap EXEC [ARGS...]"
exit 1
fi
EXEC="$1"
shift
ARGS=""
for p in "$#";
do
if [ -e "$p" ]
then
p=$(winepath -w $p)
fi
ARGS="$ARGS '$p'"
done
CMD="wine '$EXEC' $ARGS"
echo $CMD
$CMD
However, there's something wrong with the quotation of command-line arguments.
$ winewrap '/home/chris/.wine/drive_c/Program Files/Microsoft Research/Z3-1.3.6/bin/z3.exe' -smt /tmp/smtlib3cee8b.smt
Executing: wine '/home/chris/.wine/drive_c/Program Files/Microsoft Research/Z3-1.3.6/bin/z3.exe' '-smt' 'Z: mp\smtlib3cee8b.smt'
wine: cannot find ''/home/chris/.wine/drive_c/Program'
Note that:
The path to the executable is being chopped off at the first space, even though it is single-quoted.
The literal "\t" in the last path is being transformed into a tab character.
Obviously, the quotations aren't being parsed the way I intended by the shell. How can I avoid these errors?
EDIT: The "\t" is being expanded through two levels of indirection: first, "$p" (and/or "$ARGS") is being expanded into Z:\tmp\smtlib3cee8b.smt; then, \t is being expanded into the tab character. This is (seemingly) equivalent to
Y='y\ty'
Z="z${Y}z"
echo $Z
which yields
zy\tyz
and not
zy yz
UPDATE: eval "$CMD" does the trick. The "\t" problem seems to be echo's fault: "If the first operand is -n, or if any of the operands contain a backslash ( '\' ) character, the results are implementation-defined." (POSIX specification of echo)
bash’s arrays are unportable but the only sane way to handle argument lists in shell
The number of arguments is in ${#}
Bad stuff will happen with your script if there are filenames starting with a dash in the current directory
If the last line of your script just runs a program, and there are no traps on exit, you should exec it
With that in mind
#! /bin/bash
# push ARRAY arg1 arg2 ...
# adds arg1, arg2, ... to the end of ARRAY
function push() {
local ARRAY_NAME="${1}"
shift
for ARG in "${#}"; do
eval "${ARRAY_NAME}[\${#${ARRAY_NAME}[#]}]=\${ARG}"
done
}
PROG="$(basename -- "${0}")"
if (( ${#} < 1 )); then
# Error messages should state the program name and go to stderr
echo "${PROG}: Usage: winewrap EXEC [ARGS...]" 1>&2
exit 1
fi
EXEC=("${1}")
shift
for p in "${#}"; do
if [ -e "${p}" ]; then
p="$(winepath -w -- "${p}")"
fi
push EXEC "${p}"
done
exec "${EXEC[#]}"
I you do want to have the assignment to CMD you should use
eval $CMD
instead of just $CMD in the last line of your script. This should solve your problem with spaces in the paths, I don't know what to do about the "\t" problem.
replace the last line from $CMD to just
wine '$EXEC' $ARGS
You'll note that the error is ''/home/chris/.wine/drive_c/Program' and not '/home/chris/.wine/drive_c/Program'
The single quotes are not being interpolated properly, and the string is being split by spaces.
You can try preceeding the spaces with \ like so:
/home/chris/.wine/drive_c/Program Files/Microsoft\ Research/Z3-1.3.6/bin/z3.exe
You can also do the same with your \t problem - replace it with \\t.