Reading binary float data as string
in [Shell]
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From: Jeenu on 3 Apr 2008 07:36 Hi Folks, I'm wondering whether I could achieve something like this from a shell: Suppose I do this from a C program: MyFloatData = 3.513423; fwrite(MyFloatData, sizeof(float), 1, pFile); is there any way to retrieve the string "3.513243" at the shell? I would like to pass the string later on to bc or expr for processing. Thanks Jeenu
From: Janis on 3 Apr 2008 07:51 On 3 Apr., 13:36, Jeenu <jee...(a)gmail.com> wrote: > Hi Folks, > > I'm wondering whether I could achieve something like this from a > shell: > Suppose I do this from a C program: > > MyFloatData = 3.513423; > fwrite(MyFloatData, sizeof(float), 1, pFile); > > is there any way to retrieve the string "3.513243" at the shell? I > would like to pass the string later on to bc or expr for processing. $ MyFloatData=3.513423 $ printf "%g\n" "$MyFloatData" 3.51342 $ printf "%s\n" "$MyFloatData * $MyFloatData" | bc 12.344141 Is that what you want? > > Thanks > Jeenu
From: Jeenu on 3 Apr 2008 07:56 On Apr 3, 4:51 pm, Janis <janis_papanag...(a)hotmail.com> wrote: > On 3 Apr., 13:36, Jeenu <jee...(a)gmail.com> wrote: > > > Hi Folks, > > > I'm wondering whether I could achieve something like this from a > > shell: > > Suppose I do this from a C program: > > > MyFloatData = 3.513423; > > fwrite(MyFloatData, sizeof(float), 1, pFile); > > > is there any way to retrieve the string "3.513243" at the shell? I > > would like to pass the string later on to bc or expr for processing. > > $ MyFloatData=3.513423 > $ printf "%g\n" "$MyFloatData" > 3.51342 > $ printf "%s\n" "$MyFloatData * $MyFloatData" | bc > 12.344141 > > Is that what you want? > > > > > Thanks > > Jeenu I'm afraid not. I wanted to read the binary data from file. Following what you wrote: MyFloatData=$(some_command_or_commands myfile) # MyFloatData should now contain 3.513423 where "myfile" is to where the fwrite output went in OP.
From: Ed Morton on 3 Apr 2008 08:05 On 4/3/2008 6:56 AM, Jeenu wrote: > On Apr 3, 4:51 pm, Janis <janis_papanag...(a)hotmail.com> wrote: > >>On 3 Apr., 13:36, Jeenu <jee...(a)gmail.com> wrote: >> >> >>>Hi Folks, >> >>>I'm wondering whether I could achieve something like this from a >>>shell: >>>Suppose I do this from a C program: >> >>>MyFloatData = 3.513423; >>>fwrite(MyFloatData, sizeof(float), 1, pFile); >> >>>is there any way to retrieve the string "3.513243" at the shell? I >>>would like to pass the string later on to bc or expr for processing. >> >>$ MyFloatData=3.513423 >>$ printf "%g\n" "$MyFloatData" >>3.51342 >>$ printf "%s\n" "$MyFloatData * $MyFloatData" | bc >>12.344141 >> >>Is that what you want? >> >> >> >> >>>Thanks >>>Jeenu >> > > I'm afraid not. I wanted to read the binary data from file. Following > what you wrote: > > MyFloatData=$(some_command_or_commands myfile) # MyFloatData should > now contain 3.513423 > > where "myfile" is to where the fwrite output went in OP. $ cat myfile 3.513423 $ awk '{print $1 "^2 = " $1 * $1}' myfile 3.513423^2 = 12.3441 Like that? Ed.
From: Jeenu on 3 Apr 2008 08:21
On Apr 3, 5:05 pm, Ed Morton <mor...(a)lsupcaemnt.com> wrote: > On 4/3/2008 6:56 AM, Jeenu wrote: > > > > > On Apr 3, 4:51 pm, Janis <janis_papanag...(a)hotmail.com> wrote: > > >>On 3 Apr., 13:36, Jeenu <jee...(a)gmail.com> wrote: > > >>>Hi Folks, > > >>>I'm wondering whether I could achieve something like this from a > >>>shell: > >>>Suppose I do this from a C program: > > >>>MyFloatData = 3.513423; > >>>fwrite(MyFloatData, sizeof(float), 1, pFile); > > >>>is there any way to retrieve the string "3.513243" at the shell? I > >>>would like to pass the string later on to bc or expr for processing. > > >>$ MyFloatData=3.513423 > >>$ printf "%g\n" "$MyFloatData" > >>3.51342 > >>$ printf "%s\n" "$MyFloatData * $MyFloatData" | bc > >>12.344141 > > >>Is that what you want? > > >>>Thanks > >>>Jeenu > > > I'm afraid not. I wanted to read the binary data from file. Following > > what you wrote: > > > MyFloatData=$(some_command_or_commands myfile) # MyFloatData should > > now contain 3.513423 > > > where "myfile" is to where the fwrite output went in OP. > > $ cat myfile > 3.513423 > $ awk '{print $1 "^2 = " $1 * $1}' myfile > 3.513423^2 = 12.3441 > > Like that? > > Ed. Still no :) When I did fwrite in my C program, the file does no more contain the string "3.513423", instead it's 4-byte (being of type float) *binary data* - unlike fprintf. So `cat myfile` would give you only some non- printable characters. My intention is to do something in shell, what this would do in a C program: fread(&MyFloatData, sizeof(float), 1, pFile); sprintf(MyString, "%f", MyFloatData); /* MyString is of type char* */ printf("%s\n", MyString); Here, program will print "3.513423" |