Linked Questions

63 votes
6 answers
147k views

Difference between printf and echo in bash [duplicate]

What is the difference between the printf function in bash and the echo function? Specifically, running: echo "blah" >/dev/udp/localhost/8125 did not send the "blah" command to the server ...
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  • 1,711
0 votes
1 answer
713 views

How to replace `\t` with a TAB character in a string, in a way that is independent of the shell? [duplicate]

I have a script that is going to be executed by sh and bash on Debian Linux. When it is called by sh, the following echo command works perfectly, and replaces \t with 3 spaces. However, it fails when ...
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0 votes
0 answers
60 views

Avoiding echo -e [duplicate]

I would like to store an HTTP request in a variable and then use it with OpenSSL I now have HTTP_REQUEST="HEAD / HTTP/1.1\\nHost: ${HOST_HEADER}\\nUser-Agent: check_ssl_cert/${VERSION}\\nConnection: ...
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  • 9,336
0 votes
0 answers
30 views

echo a variable differs between the unix distributions [duplicate]

i have a simple shell script that echoes variable in a file but i have issues getting it work the same way between the different distributions. The script #!/bin/sh res="=1B,\=AB=D2=DB=B5=A6e=FCj=...
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0 votes
0 answers
12 views

zsh command expansion applies esacping [duplicate]

I have a string S, for which I want to replace every b character with \\ (two forward slashes). So this is what I have: $ S="abc" $ A=$(echo $S | sed 's/b/\\\\/') In bash I get the expected ...
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718 votes
5 answers
286k views

What does "--" (double-dash) mean?

I have seen -- used in the compgen command. For example: compgen -W "foo bar baz" -- b What is the meaning of the -- in there?
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  • 27.1k
304 votes
12 answers
553k views

How can I test if a variable is empty or contains only spaces?

The following bash syntax verifies if param isn't empty: [[ ! -z $param ]] For example: param="" [[ ! -z $param ]] && echo "I am not zero" No output and its fine. But when param is ...
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  • 6,623
122 votes
20 answers
310k views

How to count the number of a specific character in each line?

I was wondering how to count the number of a specific character in each line by some text processing utilities? For example, to count " in each line of the following text "hello!" Thank you! The ...
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  • 90.7k
80 votes
8 answers
116k views

How to delete line with echo?

I know that I could delete the last three chars with: echo -ne '\b\b\b' But how can I delete a full line? I mean I don't want to use: echo -ne '\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\...
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  • 36.4k
76 votes
9 answers
247k views

Can sed replace new line characters?

Is there an issue with sed and new line character? I have a file test.txt with the following contents aaaaa bbbbb ccccc ddddd The following does not work: sed -r -i 's/\n/,/g' test.txt ...
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  • 8,890
39 votes
15 answers
87k views

'ls -1' : how to list filenames without extension

ls -1 lists my elements like so: foo.png bar.png foobar.png ... I want it listed without the .png like so: foo bar foobar ... (the dir only contains .png files) Can somebody tell me how to use ...
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  • 511
72 votes
9 answers
267k views

How to add new lines when using echo

Why does the following command not insert new lines in the generated file and what's the solution? $ echo "Line 1\r\nLine2" >> readme.txt $ cat readme.txt Line 1\r\nLine2
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76 votes
8 answers
169k views

Bash: Assign output of pipe to a variable

I am trying to get the output of a pipe into a variable. I tried the following things: echo foo | myvar=$(</dev/stdin) echo foo | myvar=$(cat) echo foo | myvar=$(tee) But $myvar is empty. I don’...
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  • 761
72 votes
6 answers
189k views

Concatenating two variables with an underscore

I need to concatenate two variables to create a filename that has an underscore. Lets call my variables $FILENAME and $EXTENSION where filename is read from a file. FILENAME=Hello EXTENSION=WORLD.txt ...
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  • 1,045
72 votes
5 answers
318k views

Redirecting the content of a file to the command "echo"

I have a file named my_file.txt whose content is just the string Hello. How could I redirect its content to the command echo? I know I have the commands less, cat, more... but I need to do it with ...
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