I will be getting one command line argument in the script I'm writing which will itself be a space delimited list of the actual command line arguments. I'd like to set the arguments of the current script with these arguments. How might I accomplish that?
I'd like to use set -- but I'm not sure how this would work.
E.g.
Given arguments to my script: -a -b -c
echo $1 # prints "-a -b -c"
You can do this with set -- "${(z)1}". This will split $1 into words, handling quoting the same way the shell itself does:
% cat script.zsh
#!/usr/bin/env zsh
set -- "${(z)1}"
for arg; do
echo "==$arg=="
done
% ./script.zsh "-a -b -c -d'has spaces'"
==-a==
==-b==
==-c==
==-d'has spaces'==
If you also want to remove a level of quotes, use "${(#Q)${(z)1}}" instead.
Related
How to define local variable in Makefile target?
I would like to avoid repeating filename like:
zsh:
FILENAME := "text.txt"
#echo "Copying ${FILENAME}...";
scp "${FILENAME}" "user#host:/home/user/${FILENAME}"
But I am getting an error:
FILENAME := "text.txt"
/bin/sh: FILENAME: command not found
Same with $(FILENAME)
Trying
zsh:
export FILENAME="text.txt"
#echo "Copying ${FILENAME} to $(EC2)";
Gives me an empty value:
Copying ...
You can't define a make variable inside a recipe. Recipes are run in the shell and must use shell syntax.
If you want to define a make variable, define it outside of a recipe, like this:
FILENAME := text.txt
zsh:
#echo "Copying ${FILENAME}...";
scp "${FILENAME}" "user#host:/home/user/${FILENAME}"
Note, it's virtually never correct to add quotes around a value when assigning it to a make variable. Make doesn't care about quotes (in variable values or expansion) and doesn't treat them specially in any way.
The rules for a target are executed by the shell, so you can set a variable using shell syntax:
zsh:
#FILENAME="text.txt"; \
echo "Copying $${FILENAME}..."; \
scp "$${FILENAME}" "user#host:/home/user/$${FILENAME}"
Notice that:
I'm escaping end-of-line using \ so that everything executes in
the same shell
I'm escaping the $ in shell variables by writing $$ (otherwise
make will attempt to interpret them as make variables).
For this rule, which apparently depends on a file named text.txt,
you could alternatively declare text.txt as an explicit dependency and then write:
zsh: text.txt
#echo "Copying $<..."; \
scp "$<" "user#host:/home/user/$<"
I want to search a file and include the text #!/bin/bash, but exclude any other line that has a # sign. These two commands: grep -w '#!/bin/bash' file and grep -v '^#' file each do one part of this job. I would like this to be a single command, so here's what I've tried.
grep -w '#!/bin/bash' | grep -v '^#' file
This excludes lines beginning with #, but doesn't include the line #!/bin/bash
grep -w '#!/bin/bash' -v '^#' file
This just prints every line but #!/bin/bash
grep "^[^#]\|^#\!/bin/bash$" test.sh
Explanation:
^[^#] means starts by something different that #
\| is a or
^#\!/bin/bash$ is the exact line #!/bin/bash
So .. it looks as if you're trying to strip comments from bash files without removing their shebang.
The grep command can search for regular expressions, but isn't so good at applying rules of logic. You could do something like this:
grep -v '^#[^!]' input.sh
But you'd fail to strip comments that are affixed to the ends of lines. Note that I'm being a little more liberal with this regex, since it's entirely possible that a script might use something other than /bin/bash for its shebang. :-)
Another possibility would be to use awk. This lets you apply logic that cannot be expressed within a regular expression. For example, if you want to keep the commented line only if it is a shebang on the first line of the file, and remove all other comments, awk can express that as follows:
awk '
NF==1 && /^#!/; # if we're on the first line and find shebang, print.
/^#/ { next } # if this is a comment line, skip it.
1 # print everything else.
' input.sh
I am trying to get line count from a file like below in a ksh script. But it returns nothing :
filerecordcount= $((`wc -l <../data/act.dat`))
I also tried these :
filerecordcount= `wc -l <../data/act.dat`
filerecordcount= $(wc -l <../data/act.dat)
When i print the variable its not printing the value in the variable.
print "Record Count in .dat file : $filerecordcount." 1>&2;
But when i try the same from command prompt it returns the count
wc -l<../data/act.dat
You don't have to give the space after the = in assigning part. Use the below one. It will work fine. But don't forget to print the variable filerecordcount.
UPDATE:
filerecordcount=$((`wc -l <../data/act.dat`))
Simplify simplify. Your backquotes are doing the command expansion, and their output is being processed by $((...)) as an arithmetic expression. It's a little redundant.
filerecordcount=$(wc -l < ../data/act.dat)
No space after the =, and just one level of command expansion.
Alternately you can use process substitution:
read filerecordcount < <(wc -l < ../data/act.dat)
Or you could even do this without a subshell, using a loop:
filerecordcount=0
while read junk; do ((filerecordcount++)); done < ../data/act.dat
I want to get the last element of $*. The best I've found so far is:
last=`eval "echo \\\$$#"`
But that seems overly opaque.
In zsh, you can either use the P parameter expansion flag or treat # as an array containing the positional parameters:
last=${(P)#}
last=${#[$#]}
A way that works in all Bourne-style shells including zsh is
eval last=\$$#
(You were on the right track, but running echo just to get its output is pointless.)
last=${#[-1]}
should do the trick. More generally,
${#[n]}
will yield the *n*th parameter, while
${#[-n]}
will yield the *n*th to last parameter.
The colon parameter expansion is not in POSIX, but this works in at least zsh, bash, and ksh:
${#:$#}
When there are no arguments, ${#:$#} is treated as $0 in zsh and ksh but as empty in bash:
$ zsh -c 'echo ${#:$#}'
zsh
$ ksh -c 'echo ${#:$#}'
ksh
$ bash -c 'echo ${#:$#}'
$
For grep there's a fixed string option, -F (fgrep) to turn off regex interpretation of the search string.
Is there a similar facility for sed? I couldn't find anything in the man. A recommendation of another gnu/linux tool would also be fine.
I'm using sed for the find and replace functionality: sed -i "s/abc/def/g"
Do you have to use sed? If you're writing a bash script, you can do
#!/bin/bash
pattern='abc'
replace='def'
file=/path/to/file
tmpfile="${TMPDIR:-/tmp}/$( basename "$file" ).$$"
while read -r line
do
echo "${line//$pattern/$replace}"
done < "$file" > "$tmpfile" && mv "$tmpfile" "$file"
With an older Bourne shell (such as ksh88 or POSIX sh), you may not have that cool ${var/pattern/replace} structure, but you do have ${var#pattern} and ${var%pattern}, which can be used to split the string up and then reassemble it. If you need to do that, you're in for a lot more code - but it's really not too bad.
If you're not in a shell script already, you could pretty easily make the pattern, replace, and filename parameters and just call this. :)
PS: The ${TMPDIR:-/tmp} structure uses $TMPDIR if that's set in your environment, or uses /tmp if the variable isn't set. I like to stick the PID of the current process on the end of the filename in the hopes that it'll be slightly more unique. You should probably use mktemp or similar in the "real world", but this is ok for a quick example, and the mktemp binary isn't always available.
Option 1) Escape regexp characters. E.g. sed 's/\$0\.0/0/g' will replace all occurrences of $0.0 with 0.
Option 2) Use perl -p -e in conjunction with quotemeta. E.g. perl -p -e 's/\\./,/gi' will replace all occurrences of . with ,.
You can use option 2 in scripts like this:
SEARCH="C++"
REPLACE="C#"
cat $FILELIST | perl -p -e "s/\\Q$SEARCH\\E/$REPLACE/g" > $NEWLIST
If you're not opposed to Ruby or long lines, you could use this:
alias replace='ruby -e "File.write(ARGV[0], File.read(ARGV[0]).gsub(ARGV[1]) { ARGV[2] })"'
replace test3.txt abc def
This loads the whole file into memory, performs the replacements and saves it back to disk. Should probably not be used for massive files.
If you don't want to escape your string, you can reach your goal in 2 steps:
fgrep the line (getting the line number) you want to replace, and
afterwards use sed for replacing this line.
E.g.
#/bin/sh
PATTERN='foo*[)*abc' # we need it literal
LINENUMBER="$( fgrep -n "$PATTERN" "$FILE" | cut -d':' -f1 )"
NEWSTRING='my new string'
sed -i "${LINENUMBER}s/.*/$NEWSTRING/" "$FILE"
You can do this in two lines of bash code if you're OK with reading the whole file into memory. This is quite flexible -- the pattern and replacement can contain newlines to match across lines if needed. It also preserves any trailing newline or lack thereof, which a simple loop with read does not.
mapfile -d '' < file
printf '%s' "${MAPFILE//"$pat"/"$rep"}" > file
For completeness, if the file can contain null bytes (\0), we need to extend the above, and it becomes
mapfile -d '' < <(cat file; printf '\0')
last=${MAPFILE[-1]}; unset "MAPFILE[-1]"
printf '%s\0' "${MAPFILE[#]//"$pat"/"$rep"}" > file
printf '%s' "${last//"$pat"/"$rep"}" >> file
perl -i.orig -pse 'while (($i = index($_,$s)) >= 0) { substr($_,$i,length($s), $r)}'--\
-s='$_REQUEST['\'old\'']' -r='$_REQUEST['\'new\'']' sample.txt
-i.orig in-place modification with backup.
-p print lines from the input file by default
-s enable rudimentary parsing of command line arguments
-e run this script
index($_,$s) search for the $s string
substr($_,$i,length($s), $r) replace the string
while (($i = index($_,$s)) >= 0) repeat until
-- end of perl parameters
-s='$_REQUEST['\'old\'']', -r='$_REQUEST['\'new\'']' - set $s,$r
You still need to "escape" ' chars but the rest should be straight forward.
Note: this started as an answer to How to pass special character string to sed hence the $_REQUEST['old'] strings, however this question is a bit more appropriately formulated.
You should be using replace instead of sed.
From the man page:
The replace utility program changes strings in place in files or on the
standard input.
Invoke replace in one of the following ways:
shell> replace from to [from to] ... -- file_name [file_name] ...
shell> replace from to [from to] ... < file_name
from represents a string to look for and to represents its replacement.
There can be one or more pairs of strings.